This book requires multiple ratings.
As a book, two stars. It contains a wealth of excellent, highly useful material on the personality theory called the process communication model and how to apply it as a professional (workplace) coach. Yet it suffers from confusing organization, inconsistent and hard-to-follow formatting, bad (or nonexistent) editing, and possibly poor translation from the French at certain points. Not all self-published books betray a lack of professional support, but this one does, big time.
As to the substance, I give it both one star and five stars at the same time.
The personality model blows me away. It covers the bases of diverse human functioning more completely and more flexibly than any other I've seen, including ones I still admire and use. In particular, it is the first model I have seen that cogently describes how some people's personalities perceptibly change across powerful life shocks (that is, they talk and act differently and are sensitive to different things after a major crisis or transition) even though their underlying personality structure remains unchanged since early childhood.
On the other hand, the authors also assert a philosophical position about being human—really a presupposition or a faith claim—that I find very weak. The model claims that genuine communication between two people only occurs when each person believes both "I'm OK" and "you're OK." ("OK" isn't clearly defined.) That's probably true. But the authors go further and maintain that each person actually is "OK" all the time and that being and acting "not OK" is just a "mask," an inauthentic illusion. I'm convinced rather that the human condition is that we are each both "OK" and "not OK" simultaneously, all the time, and it's a paradox of life.
The authors also assert that if a person is getting their psychological needs met, they experience well-being. Fair enough. But the needs they identify, varying in significance by personality type—recognition for work and opinions, structured time, excitement, contact, solitude, personal recognition, and good sensory experiences—don't get to the core of human longing. Of course they're important for comfort, but if all of them are met and a person still lacks meaning, purpose, sacrificial love, belonging, identity, generativity, growth, justice, and the like, how much well-being will they really have? It's an astoundingly shallow prescription for human flourishing.