A recent article in the New York Times suggests that e-readers are finally catching on. The article is titled "Turning Page, E-Books Start to Take Hold," and it reviews the Kindle, the Sony, the iPhone/Stanza and the whole range of e-readers in terms of how they are doing. It also has illustrations of the various readers, if you're curious.
In other news, companies are working to develop even better readers, including color (but still e-ink) screens, and lighter weight readers. It looks like the e-reader has finally got momentum on its side. The interesting thing now will be how this affects book publishing.