I buy the Kindle DX from Amazon and how/where can I download free kindle books?

Below are the millions of free books and full list of bestselling books, that you can get for your Kindle:

http://www.amazon.com/gp/b/?node=2245146011&tag=elec-m-20

http://www.amazon.com/b?node=1286228011&tag=elec-m-20

And guess you know, Amazon just released a new Kindle DX Graphite with 50% better contrast and further price slash. You can read this article to decide whether to choose the original Kindle or the new Kindle DX:

http://www.amazon.com/gp/redirect.html?ie=UTF8&location=http%3A%2F%2Fwww.amazon.com%2Freview%2FR2JP0J2C8ZHYMH%3Fie%3DUTF8%26ref_%3Dcm%5Fcr%5Frdp%5Fperm&tag=elec-m-20&linkCode=ur2&camp=1789&creative=390957

Hope it helps