The Heroes of Olympus

The Heroes of Olympus is the second Camp Half-Blood series, preceded by Percy Jackson and the Olympians and written by the same author, Rick Riordan.

The first book in this series is The Lost Hero, and it was released October 12, 2010. It describes the fact that Percy Jackson, the main character from the preceding series, has been missing for three days. It shows the quest to save the Queen of the Gods, Hera, from the giant Porphyrion. Jason Grace, son of Jupiter, Piper McLean, daughter of Aphrodite, and Leo Valdez, son of Hephaestus, fly to find Boreas, the god of the northern winds on their bronze dragon named Festus. Later, along with Coach Hedge the satyr, they fight a fire-breathing giant named Enceladus to save Piper's dad. It is at the Wolf House where they manage to defeat (albeit not permanently) the king of giants, Porphyrion, to save Hera. At the end, it is revealed that Percy Jackson and Jason Grace were exchanged, as an exchange of leaders would allow each camp to gradually accept that there was another Camp Half-Blood instead of fighting each other when they met (as they have done in the past). Because Hera/Juno believes that they need both sides of demigods to unite to fulfill the second Great Prophecy and to win the war against the giants.

The second book is called The Son of Neptune and was released October 4, 2011. The book shows the quest of Percy Jackson, son of Poseidon accompanied by Frank Zhang, son of Mars, and Hazel Levesque, daughter of Pluto, to free the God of Death, Thanatos. Rick has planned five books for the entire series, and plans for them to end around 2014.

The third book planned for release in the fall of 2012 is called The Mark of Athena.

The series follows the completion of the second Great Prophecy given by Rachel Elizabeth Dare, the new Oracle after the Second Titan War. Also that is stated in one of the remaining peices of the old Sibylline Books. Gaea and the Giants are the main antagonists so far.

The Prophecy of Seven
"Seven half-bloods shall answer the call,

To storm or fire, the world must fall.

An oath to keep with a final breath,

And foes bear arms to the Doors of Death."

The Seven Heroes of Olympus

 * Jason Grace-Roman demigod, Son of Jupiter
 * Percy Jackson-Greek demigod, Son of Poseidon
 * Piper McLean-Greek demigod, Daughter of Aphrodite
 * Leo Valdez-Greek demigod, Son of Hephaestus
 * Frank Zhang-Roman demigod, Son of Mars
 * Hazel Levesque-Roman demigod, Daughter of Pluto
 * Reyna-Roman demigod, Daughter of Bellona

Books
About a week before the release of The Son of Neptune, this particular wiki released the hitherto unknown title of the third book in the series. How this was known before the second book's (at the back of which the title of the 3rd book is revealed) release is uncertain, as no known copies of The Son of Neptune were released before October 4th, 2011. Around the same time, the titles of the 4th and 5th books were theorized: The Scroll of Aphrodite and The Curse of Jupiter. However, there were no citations for this and it is unlikely that these are the actual titles of the last two books in the series.
 * The Lost Hero – October 12, 2010
 * The Son of Neptune – October 4, 2011
 * The Mark of Athena – Fall 2012
 * Book 4 – Fall 2013
 * Book 5 – Fall 2014

Audiobooks

 * The Lost Hero is available as an audiobook read by Joshua Swanson as of October 12th, 2010, with a play length of 16 hours and 34 minutes.
 * The Son of Neptune was released on October 11, 2011; a week after the book.