The mysterious book is wedged tightly into its stack, but you’re able to slowly slide it out by wiggling it from side to side. As you pull it free, you notice some light coming from the gap it leaves behind. Just after you pull it free, the books in the stack above slide down to fill the gap… and you notice that instead of having a one-book-tall gap at the top of the stack, a new book seems to have appeared to fill the gap!