We've discussed Vooks on various threads in the forum, but I think they're just a start. I think books embedded with other media have growth potential, with school books as a key.
Many readers dismiss the possibilities of media+ books now, but I think kids will grow up with them and they'll be perfectly comfortable with 'em.
As things develop, there will be good uses and bad uses of media+ books. No sense ruling out the possibilities so early in the game, I figure.