The Heroes of Olympus, Book One: The Lost Hero:    

After saving Olympus from the evil Titan lord, Kronos, Percy and friends have rebuilt their beloved Camp Half-Blood, where the next generation of demigods must now prepare for a chilling prophecy of their own:

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.

Now, in a brand-new series from blockbuster best-selling author Rick Riordan, fans return to the world of Camp Half-Blood. Here, a new group of heroes will inherit a quest. But to survive the journey, they'll need the help of some familiar demigods.