Jerry Pournelle's
Computing At Chaos Manor: November 6, 2007 includes a couple of sections on e-books. He expects the paperback market to "implode" when e-books take over as the "mass market" delivery system", and paperbacks are currently the "residuals" system for fiction (successful popular fiction has one hardback edition, but many paperback editions). He also wonders if the nature of books will change , which I agree will happen over time.