Another day another (gimmicky) way to sell books. Many years ago I tried selling remainder and sale books by the pound. It was a big success and we sold out of stock in one day. Since e-books weigh nothing, Amazon is offering the next best thing: a low-cost e-book version of any print book you've ever bought via an online retail service.
Books are a latecomer to the digital revolution. Music went from vinyl to tape to cd to digital download while books have been pretty much stuck with hardcover to paperback to the yard sale. It will be interesting to see if people really want or need both print and digital versions. Stay tuned.