Some other questions:
Would a person enjoy and be engaged in reading it as a book (without playing the game at the same time)? (thinking of its usefulness as a conversation piece, or coffee table book.)
No coverage in Adventure mode - strictly Fortress mode - although he does mention it's available. He points this out fairly early in the book while going over the different game modes so it shouldn't be a shock by the time you get to the end and there's still no Adventure mode talk. He briefly hits Legends mode as a neat way to read the history of your world, but that's it.
I would have mixed feelings over reading it as a "book" book. I do like his writing style, and there's enough humor in it to be enjoyable. Some of it is going to make more sense to someone who has hung out on b12 for a while, but still funny in a "wtf" way to new players. (Like the comments on the perpetual idiocy of your little maniacs.) Thing is, it's really a tutorial. If you're not playing along with it, or have played before, you're probably not going to really follow what he's talking about after a couple of chapters in since each subsequent chapter builds on previous ones.
I think someone reading it, with no knowledge of the game previously, is either going to be intrigued enough after a chapter or two to think about picking up the game, or confused enough to put the book down.
Regardless, I've gotten about halfway through, reading it on and off since it hit oreilly.com. I consider myself an experienced player and I am definitely enjoying it. I'm tempted to skip ahead to minecarts, since I still haven't really figured them out myself, but I'm being patient.