Rick Riordan isn't done telling stories about Greek gods. The best-selling author behind Percy Jackson and the Olympians is currently embarking on a tour for his latest book, Daughter of the Deep. That book is a riff on Jules Verne's 20,000 Leagues Under the Sea, but Riordan hasn't left his mythological interests behind. Far from it: The author will soon be returning to Percy Jackson's world, this time in a book focused on Nico di Angelo, the son of Hades who first appeared way back in The Titan's Curse.