The Invisible Library by Genevieve Cogman

What fun - Librarian Irene and her Assistant Kai travel to alternate lands/times to obtain (steal !)
important manuscripts and then bring them back to the Library for safekeeping. There is danger, there is deceit and yes dear reader, in this alternate world there are dragons, vampires, werewolves and fae at work. Librarians like Irene do have a bit of skills (magic) at their disposal but it is the elusive Kai who might have the most to hide. Fast paced and full of wit you will fall in love with the headstrong Irene, steadfast Kai and Detective Vale. This is the book for readers missing "Discovery of Witches" or "League of Dragons".