When it comes to actual people, to whom the metaphor is often applied, that is true. Books, though. Until you open them, the cover is all you have to go by! Is it a hardcover or a paperback? Is it a cardboard hardcover, or leather bound? Is it a nice fat trade paperback, or one of those weird, tall floppy ones? Does the hardcover have a dust jacket on it? Is the cover glossy or textured? Are there people on the cover picture, or is it a landscape? If there's a dog, is it the actual breed that the story describes (this you can only find out later. And, mostly, it isn't.) Does the book smell bad?
