As glued to the net as we all are, there's vast quantities of content that is not available online.
A cheap casioppeia allows me to read ebooks around 2001.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
The Kindle is already able to read more than just Amazon DRMed content, it can handle a number of formats.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.