Tacky. While I have read a book before giving it my friend knows I do this. We only saw each other a few times a year and the books were used anyway. Otherwise I just buy myself a copy as well.
I was at a Secret Santa and the person who was supposed to buy my gift just bought something for someone else because she didn't want to buy me anything. I have no idea why it's not like we really knew each other. She was new at work.