I joined the team in the spring of 1998. If an electronic book isn't readable, if you can't have the same kind of immersed reading experience that you can have with a printed book, it will never succeed. But if you can solve that problem, everything else is do-able and electronic books will become widespread.
Readability is the real obstacle.
You knock that one down and everything else happens. I think we have already proved that on screen readability can be achieved. When I first saw Reader for Pocket PCs, I thought that the screen was too small for an immersed reading experience. The ability to take your whole library and stick it in your pocket is absolutely amazing. With the version of Reader for desktop and laptop PCs, there will be a new level of readability in electronic books.