On Amazon.com today, Jeff Bezos writes a letter to customers, about reading books -- "I love slipping into a comfortable chair for a long read....The physical book is so elegant that the artifact itself disappears into the background. The paper, glue, ink, and stitching that make up the book vanish, and what remains is the author's world."

And what also remains is Kindle, the wireless portable reading device that Amazon has been secretly working on for more than three years.

With the launch of Amazon's Kindle comes the first-of-its-kind look at what could be a whole new category of wireless devices.

In the WiMax industry, which is attempting to roll out wireless broadband nationwide, there's a lot of talk about consumer devices, including cameras, MP3 players and other devices, always be connected. Sprint Nextel talks about this the most, with Kirkland-based Clearwire also saying that's a potential outcome of having always-on Internet access.

The problem with this is determining how the user should be billed. If Kindle reaches out over the wireless infrastructure for ane-book, who pays for that airtime? The user? In the form of a monthly bill that requires a two-year commitment?

At that point, adoption is almost completely ruled out.

This is why it will be interesting to see how successful Kindle is. It is adopting a new set of billing rules that Sprint Nextel talks about for its WiMax network.

In the press release, Amazon pays for the wireless connectivity for Kindle so there are no monthly wireless bills, data plans, or service commitments for customers.

The next problem is the device's cost: $399.

WiMax is also supposedly able to help with that over the long run. Its chipsets are to be more in line with Wi-Fi, rather than the costly cellular chips that the Kindle requires.

Of course, the WiMax networks still have to be built, and it has to get enough volume for this to happen.