I buy a lot of second hand books, mainly from charity shops. I check to make sure all the pages are still fixed in but other than that, I'm not bothered about the condition. This might be odd but a cracked spine and yellowy pages remind me of bookshops and trips to the library when I was little, the old dusty smell of hundreds of books stacked on top of one another. I also really like finding books with dedications or names in, it's nice to imagine what the person thought of and why it came to be in a charity shop in the first place. I've brought loads of different copies of Little Women for this reason.