Book 33: The Book of Doors. What if any door were every door? A compelling story about a world mostly like ours except there is a set of magical books that have special powers for those who have them. The Book of Pain, the Book of Joy, the Book of Memories &c. Cassie gets given the Book of Doors and discovers that there is a huge shady underworld of people who want these books and will spare no expense to get them. And of course there is a hidden library. Just the right amount of sentiment.