I've seen a few of these, and the basic minimum difference between "pulp waiting to happen" and "bookshop" is basic shelving. Different shelves by category: fiction vs non-fiction and their subdivisions. Within the shelves, alphabetise. Now it's possible for browsers to actually find things. When you put them on Amazon this will also help find them for shipping.
This process will also help you find the stacks of duplicates. You'll have a crate of 50 Shades and Twilight and Stephen King. The Stephen King will eventually resell; the others won't.
This page from the excellent Barter Books on their acceptance policy may be of some help: https://www.barterbooks.co.uk/html/About%20Us/Incoming%20Boo...