Ok guys, here's something that's gonna blow your mind. People are actually interested in this idea. I kid you not. The consensus has been that either ebooks on a mini-cd or a low capacity SD/MicrosSD card (512m or 1gb) would be perfect, plus a signing card for those who want an author's signature with the item. So we're already researching with some of the major flash OEM's (transcend, lexar, sandisk, kingston, etc) on who will give us the best deal on these, and once we have a couple cases, we're going to go about packaging them, and then seeing how they sell in general. If they don't go over well, we'll realize we got it wrong (which I doubt, given the response so far) and end the experiment there, or we'll sell out like mad and actually have to find a way to create these in bulk.
I'll keep you appraised to what happens.