Nicole Collins at The Yummy Muffin made these book sleeves for traveling:
Nicole used ¼ inch (6 mm) thick flex foam for padding and lined the sleeves for good measure.
What a great idea – your books are padded but easily accessible. And the size, shape, opening (with or without closure) and materials are infinitely customizable.
Note: I wasn’t paid or perked to mention this; just passing along a good thing.