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 preceeding series, has been missing for three days. It shows the quest to save Jason's patron, Hera, from the giant Porphyrion. At the end, it is revealed that he and Jason Grace were exchanged as both the Greek and Roman Camp Half-Blood warleaders to each camp to learn each camp's techniques of war and training. The second book is called The Son of Neptune and is coming in Fall 2011. Rick has planned five books for the entire series, and plans for them to end around 2015.

The series follows the completion of the second Great Prophecy given by Rachel Elizabeth Dare, the new Oracle after the Second Titan War. Gaea is the main antagonist, and is sleeping at the beginning of the series. However, she [assumingly] wakes up.

The Second Great Prophecy
"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."

Books

 * The Lost Hero
 * The Son of Neptune

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.