I bought this book and her second one as well, at a weekend intensive back in 1994 and they have never left my frequent reference shelf since. I am a practicing astrologer and I find them essential for filling out a more complete profile of a client. All kinds of information shows up when you populate a chart with the asteroids. For some charts, I find them amazing keys to explain the person's approach and motivations, and in some charts, they are a great additional coloration. And that's just the natal chart. She goes far beyond that.
The books are comprehensive and user friendly and a must if you are serious about wanting to understand the in-depth potential they offer on your clients or yourself. They are not a quick read, but a text book on the subject.
In Mechanics of the Future, Westcott prefaces the information with a comprehensive introduction to the process of incorporating the asteroids into your practice and how to use them in the Uranian or 90 degree dial astrology. She proceeds into full explanations of practical ways to apply asteriods in multiple methodologies with suggested practices and lots of examples.
Then the delineation of each asteroid covers the psychological and behavioral aspects as well as the typical expression of it retrograde in the chart and/or by transit. She also reminds us to incorporate the aspecting points into the picture. I find the added short descriptions of the asteroid with various other celestial bodies very helpful, not only in and of themselves but as examples of how to combine the different combinations utilizing keywords.
In the back of the book, Westcott includes keywords for the Transneptunian points; an Estimate Ephemeris for the Transneptunians from 1910 to 2005 (I don't know of that has been updated, post 2005); a Suggested Reading and Sources list, plus an Index.
I highly recommend both books, and you must expect to study them to get the full benefit of the wealth of information Westcott presents, but so worth the effort.