The Lost Hero introduces Jason Grace, who wakes up with no memory and soon discovers that he is not an ordinary teenager but a Greek demigod . Along with Piper and Leo, he sets out on a dangerous quest to rescue a goddess and stop a growing threat. The book lays the foundation of the series with Greek mythology, action, and friendship , while also introducing the connection between Camp Half-Blood and Camp Jupiter. The Son of Neptune focuses on Percy Jackson, who has lost his memories and finds himself at the camp of the Roman demigods. As he slowly regains his identity and powers, the story explores Roman mythology and themes of loyalty, courage, and leadership through a high-risk quest. The Mark of Athena brings Greek and Roman demigods together as they begin a joint mission. Annabeth’s solo quest to follow the Mark of Athena becomes central to the story. This book strongly emphasizes teamwork, trust, and strategy while raising the stakes of the overall conflict. The House of Hades follows Percy and Annabeth after they fall into Tartarus, where their strength, courage, and bond are tested under extreme conditions. At the same time, the remaining heroes continue their mission above ground. This installment highlights darker themes, sacrifice, and emotional depth . The Blood of Olympus is the final book of the series, where the heroes must prevent Gaea from awakening and destroying the world. Each character faces their destiny in a final confrontation. The story concludes with powerful themes of unity, bravery, and fate , bringing the series to a complete and satisfying close.