High Quality Content by WIKIPEDIA articles! The Sea of Monsters is a fantasy-adventure novel based on Greek mythology written by Rick Riordan published in 2006. It is the second novel in the Percy Jackson the Olympians series and the sequel to The Lightning Thief. This book chronicles the adventures of thirteen-year-old demigod Percy Jackson as he and his friends rescue his satyr friend Grover from the Cyclops Polyphemus and save the camp from a Titan`s attack by bringing the Golden Fleece to cure Thalia`s poisoned pine tree.