We're pretty impressed with what you can do with executable exe documents, downloadble or shippable on a CD with extras.
We're trying different compilers, some freewared, a rather nice one called a "Baler" out of Norway for like $20 shareware that isn't quite customizable enough for us, some really top-end $100 programs, and a lot inbetween.
We like the idea that you've got just one file, nobody can "see your work", but you can have all the links and flash inclusions and stuff, closer to a webpage than a normal book..which is EXACTLY where our heads are at on Mayan Calendar Girls.
Only trouble with CD/DVD...you end up having to have them "printed" and boxed and shipped...which ends up being just as much an expensive pain in the neck as paper books.
(And we don't really see where paper books even enter a discussion of online literture, actually. That's "meat world" this site's novels are all about online.
(Turns out, from our investigations so far, that you take a CD, and the box it comes in, and the duplication fee...and the most expensive part of the whole thing is printing the title/logo on the CD. Which is totally non-essential to the reading process, off course. But the sort of weirdness you run into in publishing and/or selling.