The Invisible Library by Genevieve Cogman

As any reader knows, it is hard to resist a story that features a secret library. Even harder to resist is one with multiple alternate realities that hold endless possibilities for exploring. What drew me to this story is not only that intriguing library and alternate worlds but the fact that each library contains different tomes of dangerous lore that needed to be hunted down. Libraries, adventure, and a mashup of genres - count me in!