It's "vook," a hideous hybrid of video and book. While we're not at all opposed to the concept, the word is so far from good it seems like it's a joke. It sounds almost dirty. Either that, or like an ethnic insult. From this moment forward, we will only use it wrapped in the quotation marks of disdain.
C'mon, Simon and Schuster! You're supposed to be word people. Try harder. (See the NYT piece on "vooks" here.)