Drop spine boxes are the most common method of housing books and other objects.  They protect the contents from dirt and dust, sunlight, and even from fire and water damage.  They are a good idea for nearly every book, whether it needs repair or not. 

Drop spine boxes are especially good for damaged bindings since they allow for the transport and storage of books without causing further damage.  At times boxing alone is the best treatment for a damaged binding.

Drop spine boxes make nice carrying cases as well.  

Here are a few samples of different boxes.  You can click on each individual image, or see all of them as a slide show.