At some point, laptop or smaller devices with high quality displays and suitable access controls for intellectual property will make the sale and consumption of books, sounds and movies through these devices practical. Audio devices, such as Apple's iPod, offer an example. Carrying around a bunch of paper is uneccessary and despite the argument that a book doesn't need a battery or a re-charge, I believe that it will be very common for people to read for work and for pleasure with the same device(s) they use daily to do their work. I don't think books are going away, of course. And if electronic reading devices have not penetrated widely enough on a worldwide basis by 2010, I will lose my bet :)
Challenge Vinton G Cerf to a bet on this prediction!