There are really two issues at play here, both of which are critically important. The first issue is the presence of and support for multimedia / interactivity in an ebook / app. The battle between HTML5, CSS3, Javascript, ePub3 and a host of proprietary formats and how they will support multimedia is a significant issue that is deserving of its own thread. It's simply too big to address in a comment. The second issue is the one I gravitated towards which focuses on an author's ability to serialize their works at a pace (and price level) commensurate with their work. The opportunity for an author to enable in-book (in-app) purchases for additional material(s) is going to become paramount to their success. The fundamental problem here, however, is that the retailer will take a significant cut of this in-work revenue which may further inhibit the author's ability to make a sustainable living from their works. There is no question that authors and publishers should be looking at how in-book or in-app purchases can be used to increase their ARPU (average revenue per user). They should be pushing the bounds in the ways their works are created, marketed, sold and consumed on a daily basis. It is only with this pushing that the edges will be clearly identified and the business models can begin to evolve to support standard of living requirements (or not, as the case may be). If the authors don't push these bounds, someone else will push them for them (publishers? retailers?) and they will lose out in the ARPU opportunity. For the record, I totally agree with Joe. I, too, would have loved to have been able to quickly reference some of the interviews, commercials, etc. and would have gladly paid "more" for the version of the ebook containing them (not just containing links to them).

This bet strikes me as very similar to the bet Microsoft made on Facebook. Everyone thought Microsoft was crazy for investing in Facebook at that level, at that time. Microsoft gained tremendous insight into social, insight it never would have been able to gain otherwise. They’ll make a very tidy return on their investment to boot. That was smart any way you look at it. In parallel, Microsoft appears to have placed a very intelligent (and relatively inexpensive) bet into not only the tablet and ebook space with Barnes & Noble and Nook - one they have not previously been able to make - but the complete digital ecosystem necessary to play in today's consumer markets. Couple this with today's XBox subscription announcement and you can see, in very short order, exactly how Microsoft is looking at changing their game.