Right now I’m only reading the books I’ve purchased from Amazon - in their format. But it can read .txt, .doc and .prc formats, too. You’ll have to search in Kindle books for the books you’re interested in.
Folks are bitchin’ about the DRM aspects of it, but I’m just enjoying the dickens out of this little wonder. Worth every penny, IMO.
I think I drooled when I watched their demo. I’d love that little thing.
(Were all your books recent? I still want to know if you can read old stuff on there too.)