Excellent series of books, which must be read from the beginning. The heroine, Irene, is a very clever, ingenious, gifted and fearless protector of the extra dimensional library. One learns more about her, and her student, Kai, reading through the series. The Fae (acknowledgement to Jonathan Strange and Mr Norrell here) , Dragons(who love order, as opposed to the chaos caused by the Fae ), and a renegade Librarian are the dangers confronting our heroine and her apprentice when they try to retrieve books for the Library across parallel worlds. I couldn't put these books down, very imaginative and off the wall. Highly recommended.