I am generally pretty careful with books, and expect people to have the same attitude towards them as I. I have lent people books and been annoyed with the state they have been returned in - usually it is general bashed-ness that is indicative of a general lack of care - you can tell they have had coffee cups rested on them and have had pages folded over and similar.
However the condition of some of my favourite books are quite poor, generally because they have been everywhere with me. Many of my favourite have even been destroyed and I am on copy no 2, or copy no 3.
I am on copy No 4 of Martin Amis' Money, copy no 2 of the collected poetry of T.S.Eliot, Copy no 3 of the middle of the journey - Lionel Trilling, Copy no 3 of Huxley's Brave New World, copy 2 of Madame Bovary and others that I don't recall.
I will write in some books to highlight passages and I have gone as far as buying a second copy to write in and kept one for 'best'
Which I realise makes me sound mentally ill, but there you are.
Generally of course I really like nice looking books in the best possible condition, but I do not hold it against a copy if through the years of careful usage and love it starts to look a little worn around the edges, as the truth about many pristine books is that they look nice because no one has read them. A tatty book which I have almost loved to death about which I can tell you that this spot was made by a glass of red wine, or that mark made by a gravy rip-tide when I dropped a big piece of steak back on to my plate, or that muddy corner of a page was acquired when I was not looking coming out of Kings Cross station and some girl in a fantastic green trousersuit knocked it out of my hand in to a puddle, is valued much more than 100 books that I haven't touched.