I was tired of the crazy look that a mismatched bunch of books gave in my guest bedroom, which has built-in bookshelves. I tried to dress it up with additional decor, but then realized it was the books that needed a makeover.
For this project, I bought plain, unbleached cotton fabric from Jo-Anns at $2 a yard. You will use a lot if you have a lot of books, so while linen sounds lovely, consider your budget! Then I just cut the fabric to match each book, and glued in the insides.
For a little extra touch, I did a Citra-Solv transfer of images (from The Graphics Fairy, http://graphicsfairy.blogspot.com/) onto the front of some of the books. I just picked some of my favorites!
I don't have a before picture for this, but trust me, it's an improvement!