First of all I'm a big admirer of John Stowell's playing so I purchased this book and DVD set with a pronounced positive bias. I received it earlier this week (7/30/11) and so far I've reviewed the entire dvd and have slowly begun working through the short book.
In the DVD the viewer is treated to some truly mind and ear opening performances along with examples from the book material. This material was written and recorded in 1999 and looks like it's been transferred to DVD from VHS. That said the material is fresh and the video and sound are more than adequate to convey Stowell's substantive teachings.
The book contains a lot of insight into his approach along with substantial practice material. While the book is short at 37 pages, the lessons are long because to be of value, his material must be worked to the point that it's integrated into one's playing, which is no small feat. In fact, this may be the longest 37 pages I've ever read. Needless to say, this is not a beginner's book. Rather it's for players who already have a working grasp of jazz and improvisation. (you can see my playing at 4thstuning on YouTube to judge whether or not my opinion has merit).
If one is interested in integrating triadic approaches and seamlessly blending alternate scales and their associated harmonic structures into one's repertoire OR just wants to know how John Stowell does it, this will be a very useful book.