I'd go even further. Why not sell a subscription pass? For $20 a month, you get unlimited access to all the books in Amazon's catalog. Each rental would expire

I'd go even further. Why not sell a subscription pass? For $20 a month, you get unlimited access to all the books in Amazon's catalog. Each rental would expire after two weeks, and you'd be free to take that book out again and again. I'd deal with the necessary DRM if this idea was implemented.