The Kindle 3, in particular, is dominating the market because:
- already the biggest company in ebooks
- with the most ebooks for sale
- with arguably the best hardware, and
- arguably the best mix of software features
- very low price
- industry leading customer service
- heavily advertised on TV in the US
It is really a miracle that anyone else is selling ebook readers in large volume in markets where Amazon is a big player. There are some negatives to Amazon and the Kindle, but a large fraction of the buying public, by luck or by careful research, have bought a very good product.