The library is one of the locations in Adventure High.
It's located inside the school in the upper right corner.
Julia normally hangs out here as she prefers studying as opposed to venturing into the dungeon.
After giving Julia the first Secret Note, you can get intel and see your slaves topless in the library. Giving her a second one allows you to see her topless. She needs three notes to save the Protagonist from Drape's trapdoor, while giving her a total of four notes (earliest possible by giving her the note from the fifth, seventh, eight and tenth floor) makes it possible to start dating her.
Barely anyone ever comes to the library as they prefer venturing into the dungeon in order to become stronger.
According to Julia, there's a ton of books there, including history, fiction and romance - something she seems more interested in than she lets on.
Trivia
- The library was the last location in the school to get an updated background - it didn't happen until version 0.38.