My grandad had a big library of books, but in his obsession of preservation, he wrapped all of their covers in gift wrap paper. It kind of defeated the purpose of having so many books in a library. You weren't able to browse them easily. I should go dive into them to take some some.
In middle school we had to make covers for all our textbooks on the first day of school (it was a school requirement, I guess to get a bit more lifespan out of the books). We used brown paper from old grocery bags.
Of course a lot of kids would then personalize their books with artwork and stickers. I guess it was that generation's equivalent of covering a laptop with stickers.
I did the same but had forgotten all about it until just now. I still put all the random stickers that accumulate throughout the year on my journal, it's a fun visual reminder of entirely random little things that happened during the year.