Right now there is only one book (Sandy-Pittendrigh below). Both the book and the software that displays it are under development. The Gallery-mode button is still buggy.
This is cool stuff. Across the net all other attempts at displaying books in HTML format revolve around "Flip Books" the require a PDF file as input.
One answer is so simple and so obvious everybody missed it. Build a hierarchical file system of HTML fragments and images. Build a CMS that displays them.
Well. I'm not going to give the rest away just yet.