Mudpuppy has learned a new word: Book! (Alternatively, "ook," or "boo-ah.") In fact, I'd say this is his first word that is definitely attached to a physical object that he can point to. You ask him where the book is, and he goes to get it. Or he will point at a bookshelf and say: "Book!"
Following in the family tradition, I guess. Mouse just announced that she is going to be an author when she grows up.