Percy Jackson, the demigod hero of Rick Riordan's bestselling Percy Jackson and the Olympians books, is back in The House of Hades, the latest addition to his Heroes of Olympus spinoff series. The series are inspired by Greek mythology and follow Percy -- son of Poseidon -- and his fellow demigods on their quests through contemporary America as well as the mythic underworld. But, as Riordan told us when we spoke with him at BookExpo America 2013, big changes are coming: he's going to base the next wave of books on Norse mythology.

And check out this interview with Riordan to go behind the scenes of his new book.