The Lightning Thief is the first book in Rick Riordan's Percy Jackson & The Olympians series. It follows Percy Jackson, a twelve-year-old boy who discovers he is a demigod, the son of Poseidon. As Percy embarks on a quest to prevent a war among the gods, he encounters mythical creatures and learns about his own powers. This action-packed and humorous book introduces readers to Greek mythology in a modern setting.