Not the shelves but books, apparently not all of them. I saw collectors of comics doing it to preserve them and be able to resell them later at a higher price, never for books.
Some people are insanely overprotective of books. I see the point of a signed copy, first editions of some rare old books and things like that, but I've seen people go nuts about cheap paperbacks.
A friend of mine borrowed a copy of 1984 I had laying around. She accidentally folder one of the pages or something, I don't recall. I don't think I've ever heard anyone apologies so much, but she REALLY loves books. It was just paperback I picked up because it was dirt cheap... I ended up giving it to her, that way it was her own book she damaged ever so slightly.
A friend of mine borrowed a copy of 1984 I had laying around. She accidentally folder one of the pages or something, I don't recall. I don't think I've ever heard anyone apologies so much, but she REALLY loves books. It was just paperback I picked up because it was dirt cheap... I ended up giving it to her, that way it was her own book she damaged ever so slightly.