The “Percy Jackson Ultimate Collection” typically includes the full set of books from Rick Riordan’s popular “Percy Jackson & the Olympians” series. This series follows Percy Jackson, a demigod and the son of Poseidon, as he embarks on adventures rooted in Greek mythology. The ultimate collection usually contains:

1. **The Lightning Thief**
2. **The Sea of Monsters**
3. **The Titan’s Curse**
4. **The Battle of the Labyrinth**
5. **The Last Olympian**

Additionally, the collection may include supplementary materials such as:

– **The Demigod Files** (a companion book with short stories and additional content)
– **The Ultimate Guide** (a comprehensive companion book with character profiles, maps, and more)

The ultimate collection often comes in a specially designed box set or slipcase, featuring artwork related to the series, and is a great way for fans to enjoy all the adventures of Percy Jackson and his friends.