Book 1
The Lost Hero (Heroes of Olympus Book 1)
Rick Riordan
Book 2
The Son of Neptune (Heroes of Olympus Book 2)
Rick Riordan
Book 2.5
The Demigod Diaries (Heroes of Olympus)
Rick Riordan
Book 3
The Mark of Athena (Heroes of Olympus Book 3)
Rick Riordan
Book 4
The House of Hades (Heroes of Olympus Book 4)
Rick Riordan
Book 5
The Blood of Olympus (Heroes of Olympus Book 5)
Rick Riordan