Some people love to categorize spiritual teachers into schools, styles and lineages, rather than focusing on the message. I suppose that if we were to categorize Stuart, it would be to call him some type of Rascal Sage.
But that would miss the point of his uniqueness. I've read thousands of books on philosophy and metaphysics, and Stuart's stand out for their clarity and compassion. He is obviously an extremely acute observer of humans and of the world(s) that we inhabit. He has many detractors, not least because he insists on trying to make people self-reliant. That has always resonated for me: the whole thrust of my own work has been to empower people and to help them find the physical, psychological, interpersonal, subtle and spiritual tools that they need to realize their full potential, enrich their lives and serve others. In one of Stuart's books he uses a good analogy: if you spend your life carrying people toward a goal, their legs will become weak and no longer support them. He points the direction to go in and some methods for getting there, but the work of getting there is yours alone.
So sometimes Stuart says outrageous things to give people a jolt, to try and shock them out their ego-based complacency. That can be painful and even a little irritating. Yet though I've never met him, I'm convinced that he usually does from the highest motives.
Looking back over my copy of this book, it is, like all of his others, festooned in underlining, notes and comments. Do I agree with everything that he says? Absolutely not. Do I think that this book is a valuable addition to a metaphysical library, or the collection of anyone aiming to grow, then absolutely yes.
This is a book full of insights and exercises. Stuart only occasionally says, "This is exercise number three, I want you to..." He is more subtle than that, and the exercises are the more valuable for it.
Be aware that the teaching style is unusual, yet also unusually powerful, and you could get a great deal from this book.