When my great-grandson was 3 or 4, he could not read yet. But, he was very interested in looking at the art on the box for a DVD or video cassette. I don't think he ever asked what the movie was about. He just looked at the art and made a decision from it as to whether he would like to watch the movie. Seemingly, he almost never decided on something and later found that he had made a mistake.
When Amazon.com or Barnes and Noble make emails and web pages about books, they usually go out of their way to show at least a thumbnail of the book's cover. I realize that book jacket design is a profession. Graphic artists apply their imagination and skills to creating just the right art for the book cover. Maybe 100 years ago, you coudn't judge a book by its cover, but today, the jacket art often gives a potential reader a pretty good idea of the tone of the book and maybe some of the plot.
The Man Who Loved Books Too Much is about rare books and the trade in them. The author relates how scams have sometimes been perpetrated by going to strong effort to create a copy of a book jacket that would have been on a first edition and putting that jacket on a much less valuable book. The story is non-fiction and the author makes clear what a market there is in just book jackets, aside of buying and selling actual books. The author also makes clear that if you are keeping a book until it is a valuable copy, you will do much better if you keep the jacket on it. With a jacket, a book can be far more valuable than without one.
