SweetLips said: "Mine--when I read a book that I love--and see it again in a bookshop, I pick it up, say to myself 'I LOVE this book' and BUY IT AGAIN !!"
I do the same exact thing! Only when I see a copy at a library book sale, though, because they're usually so cheap. I hear they shred all of the unsold books at those sales, so I do it to save my favorites from needless destruction.