As glued to the net as we all are, there's vast quantities of content that is not available online.
There are converters available from Amazon and/or Mobi for pdf and doc files.
Being at home on a rainy day, but wanting to read some new novel that just came out, you can have it in seconds. This concept (not hobbled by DRM) is pretty damned liberating.
The Kindle only allows the reading of Amazon DRM-protected content.
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.