I hate looking after books. I'm extremely rough on all the books I've read and own because a badly treated book shows that you loved it. I must've read the hobbit twenty times when I was a kid, and it shows: whole chapters have come away from the spine with the pages arranged sometimes randomly. Reading it now results in Bilbo having the ring well before he riddles with Gollum.
Hell, if I've owned a book for over a year and it's still looking new it means I either hated it or haven't gotten around to reading it yet. Books are valuable, but you have to mark the fucking things with creases, scuffs and tears, because they're experience as well.
Course, this causes all sorts of problems when I'm borrowing other people's books. I hate feeling like I'm tip-toeing around the damned things.