The Kindle is Amazon's book reader and its an amazing device, but one that I don't want yet.
The Kindle has an astonishingly readable screen (using electronic ink rather than a display tube or LCD). This means that once its painted a page there is no electricity needed to maintain the image so its always on, and the battery life is very good.
So why don't I want one of these cool devices that would let me take all/most of my books with me? Because Amazon wants me to pay for all of those books again.
As I look at my book shelves I see hundreds of books, most which were purchased from Amazon. They know this. And yet, when I buy a Kindle I have to turn around and repurchase all of those books again if I want to put them on the device. And I have to pay what amounts to full price.
When you buy a Kindle Amazon should give you and electronic copy of all they books you've purchased from them, say in the last couple of years. Until they do something like that the advertising line that you can take all your books with you simply isn't meaningful.