HTML isn’t just for the web
It’s for any text distributed online.
Technology predictions can come back to haunt you, but this one I’m sure about: The fate of non-HTML formats has been sealed by HTML5 and the iPad. People are finally noticing what was staring them in the face all along—HTML is great for expressing words. The web is mostly about expressing words, and HTML works well for it. The same holds true for electronic books.
Really interesting article filled with links to things like ePub Zen Garden - a look at different epub stylings, a crowdsourced editing project, and some other e-book projects.