This past Sunday Kirk Biglione created and uploaded a WordPress theme for iPads and tablets. It's based on Bibliotype, a freely available html template. (If you want to see the theme in action, point your browser here.) Bibliotype was released about a month ago, and it's not a commercial product so much as it's an experiment in how you might lay out a long article so it can be read easier.
If you click on the link, you might notice that this template (and theme based on it) is really intended for tablets and not other types of screens. It is. But if you're interested in designing ebooks and/or web content then I think you should check it out. There are a number of rather interesting details in how it works. For example, the font size changes but the words per line does not. I also like how you can change the background color. It's a little thing, but there are times it would be useful.