(Disclaimer: as with a lot of stuff floating around on the interwebs, this idea isn't wholly mine. I saw this ages ago somewhere and just came up with my own method of doing it)
If you make one of these, please please send me a picture! I would love to see what people come up with.
More tutorials and other crap I make & do at hungrypanda.net
Step 2: Take apart your book
Step 4: Handles/Straps
Sew the strips with the right sides facing each other, turn them inside out, fit them through the handles and sew the straps together.