"Heroes of Olympus" is a five-book series written by Rick Riordan. It is a sequel to the Percy Jackson & the Olympians series and follows a new generation of demigods. The story revolves around the quest to stop the awakening of the ancient earth goddess Gaea and features characters from both series, including Percy Jackson, Annabeth Chase, and new heroes like Jason Grace and Piper McLean. The series is set in a world where Greek and Roman mythology intertwine. Each book focuses on different quests and challenges faced by the demigods, emphasizing themes of friendship, bravery, and identity. The narrative combines adventure, humor, and mythology, appealing to young readers.