So there are, like, video games that play with the fact that you're looking at a screen, or messing with a controller. There are movies or TV that do similar things. Not enough books play with the physical medium they're in (e.g. House of Leaves). It would be cool to have more books not just user paper and ink as an incidental delivery mechanism for ideas, but as a part of the art.
@Syrus Good call. The Book With No Pictures is a simple and solid example.