Cell phones could be the ultimate mobile e-book reader, by virtue of their portability and ubiquitous nature. "There's a relatively small market for a dedicated device for reading best-sellers, and we're seeing more development on e-book initiatives for the iPhone, with offerings such as Shortcovers and Zinio for the iPhone," says Rubin. Add in the Google Book Search and Amazon mobile Kindle initiatives, and cell phones could become the next big platform for e-books, beyond the dedicated electronic-ink screens.

Rubin says that one area Amazon could potentially mine is that of electronic textbooks. "There's a tremendous opportunity for the first e-book provider that can tap into the textbook market," he says. "At the appropriate price, that could transform these devices from frequent-flyer folios into a staple in the homes of students."