I'm the same, I very rarely read a book twice. I think some of the Pratchett books are the only ones. Perhaps if I had a lot more time, or was a faster reader, I might, but for me there's always a new (for me) book that I would rather read.

I can see why people keep lots of books, but for me a book on a shelf is just a wedge of paper, I'd rather give it away and let someone else read it.