CNET had an interview with Ian Freed, Amazon's Kindle VP, you can read it over here. One of the things Freed revealed is that they believe they've got 70 to 80 percent of the eBook market:
CNET: Well, Apple's saying it's got 20 percent market share and I've heard Barnes & Noble saying it's got 20 percent as well, so that would leave you guys with...
Freed: Honestly, something doesn't add up because we're pretty sure we're 70 to 80 percent of the market. So, something, somewhere isn't quite working right. I encourage you to do some more research. Obviously, from the beginning of Amazon we've been very metrics-focused and we don't typically throw out numbers we don't firmly believe in. Take that 70 to 80 percent number and add up all the others and something somewhere isn't going to add up.
The freshly introduced third-gen Kindle eReaders seem to be selling quite well by the way, as Amazon has sold out all devices it had available for preorder. Consumers can still place a pre-order, but Amazon is now just giving you a place in line, and promising to deliver your device on or before September 4th.