Usability expert Jakob Nielsen takes a look at Kindle 2 usability in his column today:

[T]he device is best for reading long linear material, such as novels and some non-fiction. Kindle's best user interface feature is turning the page; the reading experience you design should require no other interactions.

Writing linear books simply requires a skill that all good authors already possess: the ability to keep readers immersed in the plot.

Kindle also works well for the long, narrative articles common in certain literary magazines and Sunday newspaper supplements. No surprise that The New Yorker is currently the best-selling magazine for the device.

... [But] it's awkward to interact with the device through its 5-way controller. Also, after every selection, you're doomed to wait for a sluggish response. And, once you finally get something, you get very little because of the small screen. Setting aside the header and footer areas, Kindle 2's content area is 525x650 pixels, or 341 kilo-pixels. In contrast, a mid-sized PC screen is 1280x1024, offering 999 KP of content, or the equivalent of three Kindles.

Given these constraints, navigating non-linear content on Kindle feels much like navigating websites on a mobile phone. Kindle content designers should therefore follow mobile usability guidelines for many user interface issues, including the presentation of article pages.