The Heroes of Olympus

The Heroes of Olympus is Rick Riordan's second series after the Percy Jackson and the Olympians series, and focuses on Greco-Roman mythology instead of only Greek mythology like its predecessor series.

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 and son of Jupiter.
 * Piper McLean: Greek demigod and daughter of Aphrodite.
 * Leo Valdez: Greek demigod and son of Hephaestus.
 * Percy Jackson: Greek demigod and son of Poseidon.
 * Frank Zhang: Roman demigod and son of Mars and legacy of Poseidon.
 * Hazel Levesque: Roman demigod and daughter of Pluto.
 * Annabeth Chase: Greek demigod and daughter of Athena.

Main Series

 * The Lost Hero – October 12, 2010
 * The Son of Neptune – October 4, 2011
 * The Mark of Athena – October 2, 2012
 * The House of Hades – Fall 2013
 * Book 5 – Fall 2014

Companion Books

 * The Demigod Diaries - August 14, 2012

Audiobooks

 * The Lost Hero was made available as an audiobook read by Joshua Swanson on October 12, 2010, with a play length of 16 hours and 34 minutes.
 * The Son of Neptune was made available as an audiobook, read by Joshua Swanson, on October 11, 2011 (a week after the release of the book), with a play length of 13 hours and 27 minutes.
 * The Mark of Athena was made available as an audiobook read by Joshua Swanson on October 2nd, with a play length of 15 hours and 9 minutes. ''

Trivia

 * So far two Gigantes have appeared in each book.
 * The Lost Hero - Porphyrion and Enceladus.
 * The Son of Neptune - Polybotes and Alcyoneus.
 * The Mark of Athena - Otus and Ephialtes.