We had all books stickered on the spine though, with the shelve/genre (for novels) or number (for educational books) and the first three letters of the author's name. So it wasn't overly hard and mostly worked out. People can mostly manage to match the picture and then alphabetise "DUM", so the Three Musketeers would generally find it's way back alright.

We still had walks to check though, and that's probably where my lifeling obsession with alphabetising and straightening shelves comes from. I do it even when i'm in a random bookstore, just alinging the spines with the edge of the shelve after putting a book back.