There is quite a lot of information that's been packed into this book. In fact, at times it almost appears too compressed and some topics could have used much more elaboration. In particular, the chapter that deals primarily with the possible Internet applications only brushes the surface of what could be discussed. The topics that are touched on include: Digital TV (an overview), enhanced TV, set-top hardware architecture, set-top server architecture, set-top operating systems, set-top middleware, set-top platforms, set-top application development (Intranet, Internet and otherwise), electronic program guides, and set-top smart cards. As you can no doubt tell, this is a staggering amount of material to get through in only about three hundred pages. Obviously the level of detail is not going to be terribly high, but it is worth it to get an introduction to so many different topics.
For the programmers out there, think of this ESSENTIAL GUIDE as a breadth first search. It covers a wide range of areas, but it does so superficially. As something you read once to get a feel for the terminology and the particulars, this book is quite good. But it's not very effective as a resource or a reference, because the in-depth material one would need simply isn't present. A good introduction only.