Percy Jackson fans can rest easy: this first book in Riordan's Heroes of Olympus spin-off series is a fast-paced adventure with enough familiar elements to immediately hook those eager to revisit his modern world of mythological mayhem. Clever plot devices--like gods who shift back and forth between their Greek and Roman personae--keep the book from feeling like a retread of Riordan's previous novels. Jason, Piper, and Leo, three students at a wilderness school for troubled teens, are transported to Camp Half-Blood after an unexpected encounter with evil storm spirits on the rim of the Grand Canyon. Not only do they discover that they are the offspring of ancient gods, but they also learn that they are three of seven demigods mentioned in the Great Prophecy uttered by Rachel in The Last Olympian. Wasting little time acclimating to their new lives, the three embark upon a quest to preserve Mt. Olympus and the divine status quo, by rescuing an erstwhile enemy. Rotating among his three protagonists, Riordan's storytelling is as polished as ever, brimming with wit, action, and heart--his devotees won't be disappointed. Ages 10–up. (Oct.)