The series is a *quintet*, meaning it has five books:
1. *Percy Jackson and the Lightning Thief*
2. *Percy Jackson and the Sea of Monsters*
3. *Percy Jackson and the Titan's Curse*
4. *Percy Jackson and the Battle of the Labyrinth*
5. *Percy Jackson and the Last Olympian*
However, Rick Riordan has written several other series in the same universe, including the Heroes of Olympus series which continues the story of Percy Jackson.