The information contained within is generally pretty good. The method seems perfectly usable, though fairly obvious--it's not so different from the various methods I've used over the years for making notes on paper.
That said, the book could have been cut by 50-75% and communicated all the most relevant information, but I guess a 100 page book wouldn't sell at $26. There were a lot of words devoted to repeating the benefits of the techniques and what amounts to inspirational anecdotes--useful, maybe, if you're unfamiliar with any of the productivity techniques or if you weren't very motivated to begin with (and if you're the sort of person who can be motivated by reading a maybe-true story of someone else succeeding--I'm not).
In short, if you're not familiar with this kind of productivity system and you want a whole book to teach you about it, then this book will do the job. It gives both practical advice and explanation of the principles of the system, enabling you to adapt it to your needs. On the other hand, if you're already familiar with systems like Getting Things Done and timeboxing, or the benefits of universal capture systems like Evernote, or if you just don't want to read a 300 page self-help book, then you can get a good-enough introduction to the system from the official website.