The Book of Mayhem (The Last Oracle, #3)

With two threats to the oracular bookstore Abernathy’s behind her, Helena finally feels secure in her role as custodian. But when a new danger rises, it threatens not the store, but the magi of Portland. As tensions between the factions grow, and monsters terrorize the city, the conflict tests Helena’s neutrality and requires her to solve the mystery—before she becomes the next victim.