There are converters available from Amazon and/or Mobi for pdf and doc files.
A cheap casioppeia allows me to read ebooks around 2001.
We've known for some time already that Amazon's AZW files are actually Mobi files, but Amazon didn't share Kindle's Mobi PID which would allow one to buy encrypted Mobi books for Kindle.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
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.