In The StacksScott Lynch2018

Life is always complicated for students of magic at the High University of Hazar, but the fifth-year exam is a particular challenge: each student must return one library book.

Of course, they must return it to the Living Library, a haunted collection of ten million magical tomes, a collection where the rules of time, space, weather, and reality itself are subject to sudden change. Escorted by armored battle-librarians, a group of four students must face mysteries and monsters in a fight to get their books back on the shelves in this brisk, darkly whimsical sword and sorcery tale.