Perhaps Amazon will let slip more details about this concept at the , in which it's expected to announced the second-generation of its Kindle hardware. It's certainly an exciting prospect for . Although the Kindle's e-ink screen undoubtedly makes for a more comfortable reading experience, the iPhone has some advantages of its own--including the fact that millions of people already own one.

"Some people have room for dedicated devices like Kindles, digital cameras, and iPods," analyst and Michael Gartenberg told me today. "But for others, there's an absolute convenience factor just associated with carrying one device instead of a multitude."

Gartenberg's take--and one I agree with--is that while reading a book on an iPhone might not be the absolute best experience, it "crosses the threshold of 'Good Enough.'" And it's better than Kindle in some ways, including the ability to use it one-handed and in cramped conditions. Plus, it fits in your pocket.

This move is also a great sign that Amazon sees its Kindle hardware not as the end-all, be-all of e-books, but as part of a larger ecosystem that includes Kindle-compatible book readers on other devices. "It's a smart move on Amazon's part," Gartenberg said. "They absolutely should look at devices like the iPhone and as complimentary to the stuff they're doing with the dedicated Kindle."

As Gartenberg points out, the US$359 Kindle reader may be great for heavy travelers, since you can load a huge number of books into a single, small device, but it doesn't necessarily make sense for a broad audience. Adding mobile phones to the party can broaden the appeal of the entire e-book category. (As someone who has spent this week toting around that weighs nearly as much as , I can see the benefits.)