Me and My friend always borrow things form each other since we are very close. One day I borrow a book from my friend and as I am returning it I notice that when I was using the book I had accidentally crumpled the some of the books pages and smeared some ink on a couple pages as well but the book is still usable and readable. I feel bad about it and want to pay my friend for what I did to the book. Since the book is still usable but in bad condition do I pay the friend the entire cost of the book or just give some money since the book is still usable?
If he accepts the book in return and will use it in it’s present condition, you would not be obligated to pay for a new book. Any compensation would be a goodwill gesture, but does not have to be the value of the book. If he does not want the book as it is, you would only be responsible to pay or replace with another used book, in the condition you borrowed it in, as that is the item you caused damage to.