Description Jack and Annie's summer vacation is no day at the beach! The bestselling, fan-favorite chapter-book series celebrates the summer solstice! In the paperback edition of the 31st Magic Tree House adventure, Jack and Annie are on a quest to a seaside land of mystery and myth, where they must overcome their fears and solve an ancient riddle. Magic Tree House books are New York Times bestsellers. They are known all around the world as books that inspire reading. Find out why with Summer of the Sea Serpent!