I probably wouldn't buy a book that combines the written word with multimedia experience. If I want somebody to read to me, I'll get an audio book. When I want to watch something (reading captioning doesn't count), I'll watch TV.
The only location where I can see the advantage of multimedia + the written word is in encyclopedias and such. But you would have to be able to read those off-line (and thus require a lot of space!), because otherwise it wouldn't give an added experience above the wikipedias of the internet...