I agree with the other reviews about this not being for beginners, in fact if you are new to the sport and want to learn the rules and basic structure of the game DONT buy this book. However, if you, like me, have been a keen student of the game for many years (24 years Browns fan - thick and thin - mostly thin) then this book will only hit some of the marks IMHO.
I think this book is aimed at someone who has not yet looked beyond the obvious rule structure and dynamics of the game. Starting off by telling the reader that they should watch the personnel units coming on to the field, the OL, DL twitches is all pretty basic stuff, I personally wanted more. I found that the book was basically over just over halfway through when the author started talking about teaching in the NFL.
That's not to say that that it does not have some great insights that were certainly new to me but too much was glossed over. I also thought that there was not enough diagramatical support to the schemes discussed in the book which, to someone at a stage in their learning to need a book like this, would have benefitted from greatly.
So if you have been getting in to the game for a couple of years, know the rules, basics of team assignments, but want to know the basics of what the offense and defense does and why, then this is a good book for you. If you know that stuff then I would suggest getting a much more detailed book on Xs and Os.