Judging books by their covers

I know that you are not supposed to but I find I do judge books based on their covers fairly regularly. Just recently I bought this book Kafka on the Shore by Haruki Murakami, an author I had never heard of before, just because I liked the cover design. Its got a black cat with green eyes on the cover looking at you, as cats usually do, with mild condescension. Also I liked the fact that it had 'Kafka' in the title and that it was by a Japanese author. I don't know why but ever since watching the movies Lost in Translation and Kill Bill (vol1 not 2), I have been fascinated with Japan - the samurais, hello kitty, tea ceremony, technology, karaoke, crazy anime cartoons...

Coming back to the topic, my friend told me an extreme case of how covers of books affected him. He said that until second standard he never used to do well in class, he even got 0/20 in math. Then in his second standard the cover of his science textbook had the pictures of space ships, galaxies and microscopes and he got really interested in the book and did well ever since. He also says things like part of the reason he did badly in school till second standard was that his father insisted on teaching him (I imagine something like the cartoon where Dad explaining the workings of a carburetor in Calvin and Hobbes); and that he means to learn swimming, violin, karate and get a dog as a pet all in the next few months, so I don't know how much credence I should place in his statements.