Reading library books? Borrowed books? New books? I purchased a number of the new stretchy fabric book covers found in school supplies to keep on hand to use. That way, all books I read will keep their fresh pages. The fabric is thin enough to see the title, etc through it, but still protects the book. I got a bunch of them during school sales at $.25 each.
A good idea to put one on a book you lend out as well, bright covering reminds the borrower to return it!