Well worn and falling apart, some books are too precious to replace.
Most of my books are in good condition because I am careful. I don't write in them (anymore). I don't break the spine (at least, not on purpose). I don't drop them into the tub nor dog-ear the pages.
That said, I have a number of books that are falling apart, ripped and torn, drawn in and beat up. I could easily replace them, and yet I don't. They are among the books I love the most, perhaps because each rip and scribble tells a story.