Option 1:

You can go to WalMart or anywhere that sells those storage bins that vertically organize files.  (Or, you can go the more expensive route and look in catalogs.)  Get enough for each student and make a label on the front for their names.  The book boxes will contain books that they are currently reading, books to be used for ongoing projects, and favorite books.  (You can also get them to practice labeling books by making a list of books they have in their box, in case someone needed a book they had.)  The boxes provide ownership of books, as well as responsibility. 

Option 2:

    Another way to use book boxes is to get a container that would be large enough to hold a book and artifacts, which I will discuss in a moment.  The container can range from a shoebox, to a vertical storage bin, or even a coffee can.  After the container is chosen, the student chooses a book to read.  When the book is completed, they begin to work on their book box.  The first step is to decorate the outside so that it relates to the story.  The next step is to gather artifacts that have something to do with the story.  For example, if the student read Harry Potter and the Sorcerer's Stone, by J.K. Rowling, the artifacts could include some jelly beans, a toy unicorn, a toy owl, a miniature broom, etc, and the outside picture might be Hogwarts.  Or, if the student read Holes, by Louis Sachar, the artifacts might include a toy shovel, a toy lizard, some dirt, miniature sneakers (Barbie sneakers work great), and a canteen, and the picture would be Camp Green Lake. 
    After the book box is decorated, the student can do "typical" things, like answer questions, make lists of characters, settings, problems/solutions, favorite/least favorite parts, etc. and put that in the box as well.  This step can be done before decorating, so students can get ideas for artifacts, or to prevent them from putting too much effort into decorating and detracting from completing this step.
    The finished products will be book boxes that will motivate anyone looking to read a book.