"Percy Jackson and the Olympians" is a popular book series written by Rick Riordan. It follows the adventures of a young boy named Percy Jackson, who discovers he is a demigod, the son of Poseidon, the Greek god of the sea. The series combines elements of Greek mythology with modern-day settings, as Percy and his friends embark on quests to prevent disasters among the gods. Throughout the series, Percy attends Camp Half-Blood, a summer camp for demigods, where he trains and learns about his heritage. The books explore themes of friendship, bravery, and identity, making them appealing to both young readers and adults.