I am extremely particular about caring for my quilting books (and all books). I lent a soft cover book to a friend and she told me that she had put it in a plastic cover to keep it clean. Was I horrified when she returned it still in the plastic cover but folded back with the spine broken so it would fit.
I will lend things at a class but have my items clearly named and I keep a close eye on where they are.
I can't afford to replace my quilting tools so am very particular about who uses them.