The dark archive / Genevieve Cogman.

"A professional spy for a mysterious Library that harvests fiction from different realities, Irene faces a series of assassination attempts that threaten to destroy her and everything for which she has worked. Irene is teaching her new assistant the fundamentals of a Librarian's job, and she is finding that training a young Fae is more difficult than she expected. But when they are the targets of kidnapping and assassination attempts, she decides that learning by doing is the only option they have left. . . . In order to protect themselves, Irene and her friends must do what they do best: search for information to defeat the overwhelming threat they face and identify their unseen enemy. To do that, Irene will have to delve deeper into her own history than she ever has before, face an ancient foe, and uncover secrets that will change her life and the course of the Library forever"-- Provided by publisher.