My kids always loved their waterproof books. We always had several of them around to use not only in the bathtub, but they were great to pack and take other places because they are so heavy duty.
You never had to worry about the pages getting torn. If you spilled juice or milk on them, they were so easy to wipe clean. They are usually bigger and take up more space than other books, but if you only have a few of them that doesn't really matter so much.