I had an order for custom book cover on my etsy.
She needed a cover to protect her books from dust and cat/dog hair. I got some plastic from the upholstery section at Joann's and made it the size she needed... 7'x4.5"x7"
Here are a few pictures of it filled with books after I finished it:
I cut vertical slits every ten inches to allow easy access to the books.
I'm also in the process of making a similar cover for a couple of strollers, to keep them clean while they are stored in the garage.