I'm a fretless electric bass player, and I've played in jazz/fusion bands with competent, formally trained musicians for a few years. I can improvise walking bass lines freely over fast-moving chord changes, and can do some modal improvisation. I also studied classical piano for 8 years. So, I approached this book with the intermediate knowledge the author says you need to understand it.
I'm also a university teacher with about 12 years of experience teaching non-music courses.
With this background, I think a good text has the theory explained in simple concepts, with many very clear examples. A good book also has a significant number of practice exercises after each theory section. These exercises should allow the student to master the individual concepts, integrating them later on. The practice exercises should also provide answers, where applicable, so you can check your work.
Further, a good book presents material so the student sees an increase in their ability to improvise as quickly as possible -- this increases their motivation to persist with the remaining exercises in the book.
Against these criteria, I find Building a Jazz Vocabulary to be a fair, but not excellent book.
Its premise -- that there is a common jazz vocabulary that the students can use to "imitate, assimilate, and innovate" is interesting and sound. The author's explanations of the components of this common vocabulary are well explained, and he provides for simple and multiple examples often.
On the other hand, I found the book to be sorely lacking in carefully crafted practice exercises that help the reader practice the concepts. The author provides Etudes (studies) but they are long and sometimes complicated. Further, there are times there are no chord changes over the staff, which makes it hard to understand how the notes fit in with the overall harmony of the song. The author repeatedly puts the onus on the reader to find their own practice exercises, with exercises like "find a jazz solo and analyze it for four-note cells". Also, there is no CD with the book, so you have to use your own play-along software like Band in a Box if you want to practice at home, which will cost you an extra $50-60 or more if you don't already have it.
In terms of providing motivation, I also found the book wanting. Like many books on improvisation, the author insists that one must learn a concept in "all keys" immediately. This presents the reader with an instantly boring and daunting task, which has no immediate return on investment. I think the author would have done better to provide play-along exercises in concert keys C, Bb and Eb, throughout the entire book. This would help the reader see some results immediately, which would further his or her motivation to keep practicing with the book. At the end of the book, he could have then encouraged the student to extend the knowledge gained to all other keys.
I think there could have been some theoretical, written practice exercises too, with answers provided.
So, this is a book a good theoretical reference -- exposing the elements of basic jazz vocabulary in a fairly well-explained and simple fashion. But it doesn't put enough effort into providing you with practice exercises to help you get the concepts into your mind and hands.