I used to volunteer to "read" library shelves at a school library. That means making sure the fiction is all correctly alphabetized by the author's last name, biographies by the subject's last name, and non-fiction by the Dewey Decimal System.
Unknown to the librarian, the library had two copies of the same biography of Mark Twain--one under "Twain", the other under "Clemens"--his real last name. Also, I found a copy of a Marco Polo biography that was at least fifty years old and apparently had never been taken out.
Books about certain subjects, such as cars and horses, were more likely to be at least slightly out of order than books about less popular subjects, such as the weather and history.