I am one of the rare old birds that don't read books.......I listen to them. But I don't know if other cities/states have what (St. Paul, Minnesota) we have and they are growing by leaps and bounds, like one or two on a block. WE have little houses in our property on a post and people put in their already read books and someone else can come and take a book or two and when they are done they can put it into another book "house". These houses are just adorable. I don't know if they are available to buy (they are on a 3-1/2-4 foot post and pounded into the ground, or if these people just make them. They are really cute. That way it's an all around share, books are changing all the time. Would be nice if they had them for audio books! Back to your book bag - I think it is a fantabulous idea. My sister belongs to a book club and has for many years and loves it. She has a book bag too. I have a book bag - it is plastic and says "I heart my Library". Hasn't worn out, but perhaps I can make me one to fit the audiobooks.
Have a good day. Edie