In any case, ideally, any ebook solution should have all resources loaded as files relative to the current document, and nothing inline. Like this, the book would be compatible both offline and to be hosted online, without requiring any changes to the book.
The one file thing is cool, but again it requires JS to show anything, so that's not really inline with what I was talking about. In my view, an HTML document should work like a book, and any JS is purely to augment and extend that book if necessary. Those situations are rare though, and most JS is just to give a reader like experience.
I think if someone is going to go through the trouble to host a book, they probably don't mind unziping a file before putting it on their server. The one file thing I said earlier was more about sharing the book, similar to an app package. but once it's on someone's servers presumably it's ready to be read.
Basically .webarchive