Several of the blogs I follow have featured this video from design firm Ideo, which demonstrates three conceptual models for "books" in the digital age (you may need to double click on the video to see it full-sized, or click on this link :
I'm a long-time Ideo fan and think they are some of the smartest designers around, but I admit I have a bit of trouble getting my head around the idea of a non-linear plotline that evolves based on the readers activities. Of course as we know, and this image from the Paleo-Future blog via Execupundit reinforces, not all predictions get it exactly right. On the other hand, if you read the text that accompanied the cartoon some of the predictions weren't so far off after all!
Whether the Ideo designers are right or wrong I think it is great that they are willing to direct some of their creative energy to the discussion about the future of the book.