Hey man, hows it. For what its worth here is my 2 cents worth: First, look around yourself - this forum - the downloads area says it ALL. If its a digital product chances are you can come across it here - for FREE. That in mind, most (if not all) digital products are worth hardly anything. Due to their DUPLICATABILITY (if thats even a word - but you know what I mean) E Books sell for, like, 7 bucks. If you want your book to retain value, without turning into a full on internet marketer (unless you are prepared to do that) in order to make a lot of money from it, then, my 2 cents worth says MAKE IT ONLY A HARD COPY. Either that or create a learning course out of it, with a fully blown website, and THEN trow some PPC at that - Just make sure all your material is website based, use a membership script, like membershipease or DDL and see how you go.
Hope this helps
Regards and Respect - for coming to this forum and having the balls to ask