Long time ago I posted about buying plastic book covers that are used on book jackets to protect them. I bought a box of 25 and almost all are used up on novels that I love and bought (used), recipe books, bird books, and other nonfiction books that reference one thing or another.
There's a popular company that sells them online - Demco is the one I think a lot of libraries use, but I got mine from Vernon a little cheaper.
I recommend these covers. They add years to the life of a book.