I did the same thing today. I PR'd 10 books and nothing interested me so I didn't buy any of them. I don't think you did anything wrong. Maybe you had no real interest in what you read or you already knew it and weren't moved to dip into anything. I picked up a book called "The internal power of the martial arts" and quickly saw it was stuff you had to practice and I was already doing most of it so what the heck do I need to buy it for? I dipped alot into things I didnt' recognize. I think if you didn't dip into anything you don't need the books. I PR'd a bunch of music books once and found one with stuff I didn't know but I remembered the topics and can now go to the library and find info on them separately for FREE. Is this ethical?