I decided, for us, to use the term 'online Book' (which I shortened to oBook).
I edited the Wikipedia entry about 'online Book' (which they had defined, wrongly I think, as an eBook that could be downloaded) to reflect this.
Specifically, I said there that an 'online Book' is a book that can only be read while online (as opposed to an eBook that can be downloaded).
I also added an entry on Wiktionary about the term oBook.
That seems to work for us at least.