However, it's interesting to note that ebook appps for the iPhone have taken off. Keep in mind that the apps are usually free, but even then, the O'Reilly Radar blog says book app “purchases” have gone up 280 percent in just 12 weeks. That's a huge increase, and it has made Books the fastest growing category of iPhone apps.
Kindle for iPhone is leading the book app pack, but there's no way to know if that's because a lot of iPhone users also own Kindles, or simply because it's so easy to buy books through the Kindle store even if you use an iPhone.
On a related note— but for a different device— Simon & Schuster cut a deal with GoSpoken.com, a UK-based digital and audio book company, to sell ebooks for Blackberries. So, ebooks grow in the Blackberry patch, too.