Riordan Wiki

This is a comprehensive list of the differences between the film and the book.

Book Film
Annabeth Chase and Percy Jackson are 12 years old. Annabeth and Percy are 16, since The Sea of Monsters film states that the Great Prophecy comes true at 20 years old.
Annabeth has curly blonde hair, and gray eyes. Annabeth has iron-straight brown hair, and blue eyes.
Annabeth's family life is mentioned. Annabeth's family life is not mentioned throughout the movie, although she did tell Percy that she grew up at Camp Half-Blood, similar to what she said in the book, and how she'd only been in the outside world a couple of times.
Luke Castellan has a scar down his cheek from a dragon attack. Luke had no scar at the beginning of the film, but received a cut on the cheek when Percy slashed him with his sword.
Clarisse is the camp bully at Camp Half-Blood. Clarisse does not appear in the film. She does appear in the Sea of Monsters film however. Certain elements of Clarrise's character are combined with Annabeth in this film, in that Annabeth is a strong warrior and has a rivalry with Percy.  
Percy fights Echidna and her Chimera atop the St. Louis Arch, the Minotaur on top of Half Blood hill, Procrustes at a water bed store, the three Furies multiple times, and encounters Cerberus at the gates to the Underworld though he didn't fight him. Percy fights the Minotaur at the entrance of Camp-Half Blood. He also fights the Hydra at the Parthenon in Nashville, Tennessee. The Hydra expels fire instead of acid. Percy also encounters a Fury (Mrs. Dodds a.k.a. Alecto). Yet Alecto's sisters, Megaera and Tisiphone, are never mentioned. Also, there was no Cerberus, Chimera, Echidna or Procrustes in the movie. Though there are three Hellhounds that Percy & co. encounter in the Underworld.
Tyson makes Percy a shield wristwatch in the second book, The Sea of Monsters. Percy already has a compact shield that is given to him by Luke. The shield has a secret compartment which held Zeus' Master Bolt.
The Hydra only appears in The Sea of Monsters. The Hydra appears in the first movie.
Persephone is with her mother because it is summer. Persephone is shown being held hostage by Hades, despite it being summer.
Percy, Grover, and Annabeth take a taxi from the Lotus Hotel and Casino. Grover, who is driving the car, bursts through the Lotus Hotel and Casino doors with a stolen Maserati.
By taking the green credit cards, Percy, Grover, and Annabeth were allured to staying in the Lotus Hotel and Casino. By eating lotus-shaped hors d'oeuvres, Percy, Grover, and Annabeth were allured to staying in the Lotus Hotel and Casino. The flowers dull the senses and keep a person prisoner.
Ares has a main role in the book, serving as the secondary antagonist, having a fight with Percy at the climax of the book. Ares only appears at the meeting in Olympus. Another scene with him was filmed, and featured very concisely in the trailer for the movie, but was cut.
Cabins have specific features catered to their patron god and in a U shape. Cabins consist of various tents and are scattered throughout the woods. They still have the specific features from the godly parent of the demigod/s living there
Riptide is a celestial bronze sword and appears to mortals as a cap pen. Riptide appears as a click pen and is never named. Though in the Sea of Monsters film, you can see Riptide's Greek name
Percy and Annabeth are trying to be friends and work together. Percy and Annabeth seem quite attracted to each other. The ending has a scene where they kiss when they battle at the end of the movie.
Medusa is fought by looking at her through a glass ball. Medusa is seen through the reflection of an iPod Touch.
Percy does not own any type of electronic device, because they attract monsters. Percy has an iPod Touch.
Percy's trident sign is like a hologram and is shown after Percy defeats the Ares campers using extra strength gained by him being in the water. Percy is not claimed in the film. He is introduced as the son of Poseidon from the start.
Luke mentions having met his dad once. Luke mentions to have never seen his dad, but all the same, he hates Hermes' guts.
Grover walks with a limp but runs "like the wind" when using mortal outfits. Grover walks with crutches and is barely shown running in the movie, except when he was running away from Medusa and the Minotaur.
Percy discovers Luke's betrayal at Camp Half-Blood and nearly dies due to the scorpion sting from Luke's scorpion. Percy learns of Luke's betrayal on top of the Empire State Building and fights him. Luke is almost close to death at this point, but nevertheless appears in The Sea of Monsters film.
Annabeth is a good warrior and strategist, and fights using a celestial bronze knife. Annabeth is a good warrior and fights using swords, bows, crossbows, and uses her knife at the end. 
Annabeth first meets Percy when she was nursing him back to health after the encounter with the Minotaur. Annabeth first sees Percy when Grover was showing him around the camp. Percy and Annabeth encounter each other a second time when they fight each other in Capture The Flag. They formally meet at the banquet after the Capture the Flag game. A deleted scene, however, depicts the two meeting at the infirmary, and the nectar from the scene is also seen being drunk.
Medusa is an old, Middle Eastern woman, with coffee-colored skin. Medusa appears to be a young, Caucasian woman.
The campers wear orange t-shirts with "Camp Half-Blood" written on them. Campers are shown to wear armor during training and Capture the Flag and modern clothing at other times
The only gods that appear in the first book are Dionysus, Ares, Hades, Zeus, Poseidon and Hestia(though Percy thought she was just a young girl at the time while she was tending a fire). Hera, Demeter, Apollo, Athena, Aphrodite, Hermes, Hephaestus, and Persephone also appear in the film. Dionysus is barely seen at camp at all.
Annabeth is on the team with Percy during Capture the Flag. Annabeth is on the other team against Percy during Capture the Flag.
Percy shows signs of being the son of Poseidon by causing the water in a water fountain to well up and "attack" Nancy Bobofit and when his fighting ability is increased after pouring water on his head. One of the signs that Percy is the son of Poseidon is his ability to hold his breath for an unnatural period of time underwater and that he "likes being in water". 
Percy has barely any control over his powers. Percy can manipulate his powers like the way he can in The Battle of the Labyrinth.
The gods usually wear normal clothes. The Gods, except for Hades and Persephone, wear Greek armor and/or togas. However, when assuming mortal guises, they don normal attire.
The key to the elevator that leads to Olympus is a card. There is no key, but a set of buttons Sally Jackson pushes to open the elevator to Olympus.
Percy and Annabeth do not get near a swimming pool. At the motel pool, Percy heals a bruise on Annabeth's arm. Afterward they discuss their relationship with their immortal parents.
Percy never wears the flying shoes that Luke gives him because of Zeus' warning of a Poseidon's son in his sky. Instead, he gives them to Grover for him to wear. The shoes were just a trick because they were meant to drag you down to Tartarus. Percy uses the flying shoes to obtain the pearl in a crown atop a statue of Athena at the Parthenon. He also uses them throughout the fight over the Master Bolt with Luke, until one wing gets cut off.
Medusa wears a black veil to cover her eyes. Medusa wears black sunglasses to cover her eyes and a wrap over her head.
Luke never fights Percy with the Master Bolt. Luke and Percy fight over the possession of the Master Bolt, using it on each other during the process.
Hades wears black, silky robes. Hades wears Gothic rock star-like clothes. (Grover refers to it as the Mick Jagger style).
Medusa's head is mailed to Olympus after Percy decapitates her. It is implied that the head was shipped to Gabe and he got paralyzed as he does in the movie. They keep the decapitated head, and Grover later uses Medusa's head to turn the Hydra into stone and Percy leaves it in his refrigerator to be discovered by Gabe.
Percy goes to Olympus alone. Percy and Annabeth go to the Gods' throne room, while Sally is left behind in the elevator.
Athena speaks with an American accent. Athena speaks with an English accent.
Hades is cold and unfriendly. Hades is made to appear somewhat humorous.
Hades dislikes the Olympians, but does not make an obvious attempt to overthrow them. Hades wants to use the bolt to become king of the gods.
Kronos is heard speaking throughout the story as a prisoner in Tartarus (in the Underworld) and is mentioned as Luke's boss. Kronos is never heard of but merely mentioned by Chiron at the beginning of the film. The plan to overthrow the Olympians is apparently Luke's in an attempt to make a new race of gods.
Percy fights Ares on the beaches of Los Angeles. Percy fights Luke in New York. Ares does not have a role in the movie.
Hellhounds are large demonic dogs. Hellhounds are medium-sized rodent-dog hybrid creatures that only understand Greek.
Sally is left behind in the Underworld and then released by Hades. Grover is left behind in the Underworld with Persephone and an unconscious Hades, but is later released by Zeus.
Mr. D is in charge of Camp Half-Blood. Mr. D was not shown in the movie. He only appears at the Council of Gods at the end of the movie, as Dionysus. He does appear in the Sea of Monsters film however.
Sally turns Gabe into stone using Medusa's head. Sally kicks Gabe out of the apartment. When Gabe comes back to reclaim his belongings, he breaks open the refrigerator to get a beer, but instead finds Medusa's head, which turns him into stone.
The gods are about 15 feet tall while in Olympus. The gods are giants over 60 feet tall while on Mount Olympus; however, it is shown that they can shrink to a normal size.
Each of the gods has their own customized throne. The gods' thrones are all the same.
The Oracle of Delphi gives out prophecies and quests. The Oracle is never incorporated into the movie, though she does appear in the Sea of Monsters film. Also, Percy is never given the quest but disobeys Chiron's orders to stay in the camp.
Argus is the many-eyed security guard. Argus never appears in the film.
Luke injures Percy and leaves for Kronos' army. Percy beats Luke and hurls him into the sea.
Thalia's Tree and her story are told. Thalia Grace is mentioned by Grover in a deleted scene. The tree is still not referred to, but her history remains the same, hinting to a role in possible sequels as in the books. There also appears to be a pine tree just outside the gate to the camp. The story is told by Percy at the beginning of the Sea of Monsters movie.
The Big House is an important place. The Big House is shown once when Percy first arrives inside Camp Half-Blood. It is prominently featured in the Sea of Monsters movie, however.
Grover is shy and very clumsy. Grover is outgoing, funny, and shows an extreme interest in women.
Yancy Academy is a private school. Yancy Academy is a public school.
Mrs. Dodds is a pre-algebra teacher. Mrs. Dodds is a substitute teacher in English.
Percy is at Camp Half-Blood for two weeks before his quest. The day Percy arrives at camp, he sneaks out for his quest.
The Pact of the Big Three is a main focus. The Big Three pact is not mentioned, but Chiron says that the children of The Big Three are rare.
Luke is given his flying shoes for his quest from his father. Luke steals the shoes from his father's house.
There is to be no technology whatsoever at Camp Half-Blood because they attracted monsters. Luke's tent is decked out with HD TV's, a couple of game systems, and an Apple computer, all of which (that can be assumed) he snuck into camp.
Poseidon left before Percy was born. Poseidon left when Percy was seven months old because Poseidon was becoming too "human".
The Minotaur has Fruit of the Loom underwear. The Minotaur has no clothing.
Sally kept her maiden name, Jackson. Sally is referred to as "Sally Ugliano", which is Gabe's family name.
No one knows who Percy's father is until Capture the Flag. Everyone is well aware of who Percy's father is except him (until he arrives at Camp Half-Blood).
Percy, Annabeth, and Grover use an Iris Message to contact camp. Annabeth FaceTimes Luke with her Apple laptop with a question regarding the flying Converse shoes.
There is quite a bit of detail regarding Annabeth and Luke's past. There is no mention of their past whatsoever, so Luke's betrayal seems irrelevant, except for the fact that he was angry at the gods, though the Sea of Monsters movie sheds some light on their past.
Percy, Grover, and Annabeth check into the Lotus Hotel and Casino. Percy, Grover, and Annabeth never check in at the hotel.
Camp Half-Blood is fairly spread out, over strawberry fields. Camp Half-Blood is crammed and in the middle of a forest.
Percy, Grover, and Annabeth meet Ares and go to Denver. They never encounter Ares and do not go to Denver. Instead, they go to a replica of the Parthenon in Nashville, Tennessee in search of one of the three pearls following Luke's map.
Sally makes blue food as a sign of defiance. There is no blue food.
The Three Fates appear before Percy and cut a blue string. The Three Fates are never seen or mentioned. Only Alecto is seen.
Cabin Three was most likely built by campers. Percy's father, Poseidon, built the cabin for him.
The Underworld's entrance is in a production studio. The Underworld's entrance is at the Hollywood sign and opens when one reads the phrase: "Woe to all Depraved Souls".
Percy is given the pearls by one of Poseidon's Nereids in Santa Monica. Persephone has three pearls hidden in America for her visitors to escape the Underworld.
Percy, Grover, and Annabeth encounter Procrustes in a water bed shop. They never encounter Procrustes or go into a water bed shop.
Annabeth has met Athena and her mother has helped guide her. Annabeth says that she has never met her mother until she went to Olympus with Percy. She did mention that her mother talked to her telepathically to guide her.
Percy and Sally were on a summer trip to Montauk Beach using Gabe's car. Percy and Sally never go on their trip. They go straight to Camp Half-Blood with Grover after a Fury attacks Percy.
Percy attacks Mrs. Dodds using Riptide. Chiron threatens to hurt Mrs. Dodds. She flees, crashing through the museum window.
Mrs. Dodds asks Percy to speak with her privately because he attacked Nancy Bobofit. Mrs. Dodds asks Percy to speak with her privately after he correctly reads a stone statue that says "Perseus Defeating Cetus," in Greek, not because of the incident with Nancy Bobofit. Also, Nancy Bobofit only has a small part in the movie, where she only accuses Grover of "being a perv", toning down her bullying from the book. She is also Asian, unlike in the books where she is Caucasian.
Percy promises to come back to Camp Half-Blood next summer at the end of the book. At the end of the movie, Percy is seen staying at camp, possibly year-round.
Medusa's body dissolves leaving the head. Medusa's body does not dissolve as the heroes take the pearl and head.
Percy breaks off the Minotaur's horn and uses it to kill the Minotaur. The Minotaur breaks its own horn off after running into a tree. Percy pulls it out and stabs the Minotaur with it.
The Minotaur dissolves after Percy kills it. The Minotaur does not dissolve after Percy kills it.
Percy, Annabeth, and Grover use the ransom of a pink poodle named Gladiola to get money for a train ride across the country. They never encounter Gladiola and instead drive across the country but there is a poster of him hung up.
Percy, Annabeth, and Grover ride in the back of a zoo truck found/provided by Ares to Las Vegas, in the end releasing the mistreated animals. The zoo truck never appears and is never mentioned; instead the three drive across country following Luke's map.
Hades' Helm of Darkness was also missing. Hades' Helm of Darkness was never stolen or mentioned.
Percy encounters a Hellhound in the forest at camp. Percy never encounters a hellhound in the forest. Instead, a demonic form of Hades appears from the campfire and tries to persuade Percy to give him the Master Bolt. Three Hellhounds are encountered when Percy & co. enter Hades' lair.
Percy is called "Seaweed Brain" throughout the story on various occasions by Annabeth. The nickname "Seaweed Brain," is never used by Annabeth or anyone else.
Annabeth owns a Yankees cap of invisibility (a gift from her mother Athena) that she uses constantly. Annabeth is never seen with such cap and instead ambushes Percy at the red flag's location (by hiding in bushes/trees and jumping down to meet him).
Clarisse attacks Percy during the game of Capture the Flag. Annabeth attacks Percy while he is trying to get the flag.
The shoes 'activate' when you say the word 'Maia'. According to Luke, the shoes activate when you have a running start like a plane on a runway.
Grover explains to Percy why Sally married Gabe. Chiron explains to Percy why Sally married Gabe.
Percy hears Kronos speak to him in his dreams and asks him to join him in his war against the gods. Percy does not have dreams and only hears his father's voice guiding him.
Percy believes that Hades stole the bolt. Hades is never accused of stealing the bolt. Percy's purpose in confronting Hades is to get his mother back from the Underworld.
Percy never gets wet unless he wants to. Percy gets wet when in water. But, in the Capture the Flag scene, after he heals himself, he is dry.
Camp Half-Blood's borders include strawberry fields and Thalia's tree. Half-bloods have the power to let others enter the borders like Annabeth did for Tyson in the Sea of Monsters. Camp Half-Blood's borders include a forest and a magic gate with a huge sign saying: "Camp Half-Blood." Grover would have known how to allow someone in and did not allow Sally in.
Cabin Three is made up of seashells and is decorated with corals, and seemed to be filled with ocean's air that smells "salty and cool." Cabin Three is isolated from the others. It sits on the lake (or ocean, not exactly specified in the movie) and is an open-walled "cabin" with a cloth roof, built by his father, Poseidon. It seems to be made out of wooden pillars. It is furnished to look like a sea captain's study.
Percy is directed by Annabeth to be the border patrol on the left flank next to the river in the woods. Percy teams up with Luke to attack and capture the flag. He is directed to keep going when they encounter resistance from the red team.
The lower half of Chiron's body is described as being a white stallion. The lower half of Chiron's body is shown as having brown fur.
Chiron reveals himself to be a centaur when he and Percy are at the Big House. Chiron is revealed to be a centaur when Percy sees him galloping on the beach with other centaurs.
Chiron uses a bow and arrow when he fights. When Hades appears at the campfire, he used two swords.
Chiron is the only centaur at Camp Half-Blood. Other centaurs were seen (together in a herd) roaming along the beaches of the Camp with Chiron. It's possible these are the Party Ponies.
Annabeth, Percy, and Luke are all on the blue team during Capture the Flag. Clarisse is on the red team. Percy and Luke are on the blue team whereas Annabeth is on the red team. Clarisse does not make an appearance in the movie whatsoever.
Luke is shown using the sword "Backbiter" at the end of the book. Luke never wields Backbiter during the movie.
Annabeth has a necklace consisting of 5 clay beads that mark each of the years she has spent at Camp Half-Blood. She also has a college ring (her Dad's) attached. Camp necklaces are neither seen nor mentioned.
Percy and Poseidon have black hair and green eyes. Percy and Poseidon both have blue eyes, and Percy's hair has dark brown hair and Poseidon's is light brown/blonde.
The Mist is a central part of the mythology's secretive world. It plays a major role throughout the books in either hiding or disguising what an object really is or what is really happening. It is essential in keeping the mortal world in order. In the movie, however, there is no mention or active presence of the Mist. When Grover holds up Medusa's head in the motel, a passing maid sees the severed head and is surprised and runs. Also, the monsters simply transform from a human form into their monster form (for example, the Hydra is represented by multiple security guards until they transform into the hydra). However, in The Sea of Monsters film, Mist does exist (albeit as a spray can).
The Master Bolt is in a cylinder of glass capped with celestial bronze. The Master Bolt is a crystal-like lightning shaft able to be carried by anyone.
Only Poseidon and Zeus are shown on Olympus after Percy completed his quest. All the Olympians are shown on Olympus.
In the Underworld, there are shown the different areas of the afterlife, such as Elysium, Asphodel, Tartarus, and the Fields of Punishment. None of these are shown, and instead the Underworld is a fire-drenched, burning version of Los Angeles (i.e. The Hollywood sign now reads "Hell"). Charon even makes clear note that all lives end in suffering and tragedy.
Percy and Annabeth go on the Thrill Ride O' Love in Waterland to retrieve Ares's shield. Percy and Annabeth did not do the Thrill Ride O' Love in Waterland, and Waterland was not even mentioned in the movie.
In the museum, Percy is interested in the lecture that Mr.Brunner/Chiron is saying about the artifacts. In the museum, Percy is not interested in what Mr.Brunner/Chiron is talking about. He has headphones on when Chiron asks him a question.
Grover is Caucasian.  Grover is played by Brandon T. Jackson, an African-American actor.
Grover has protected many demigods, such as Annabeth, Luke, Thalia, Percy, Nico, and Bianca. Grover states that he is a Junior Protector while apologizing to Percy about his mother's kidnapping earlier in the infirmary. His backstory about protecting Thalia (and Annabeth & Luke) is mentioned in a deleted scene, however. 
Grover already had horns in the story. Grover does not grow horns until the end of the film.