"By the way, did you know that the primary shelving sort for books in the Library of Cngress is by height?"

That's how we sort the books in the off-site storage library for the library where I work. It's kinda creepy going in there; the shelves are mechanical and the push of a button will move this entire huge range of shelving to one side or the other for a book to be retrieved. I helped move some of the books to that site last year. Each and every volume has its barcode keyed in along with the one for the shelf so its "address" can be looked up in the event some hapless fool wants to check it out. I have no idea how involved the check out procedure is for storage books; I work in a building with windows and desks and shelves that stay put. Mostly. We've had to add a few robot shelves as space gets tighter...