Is this work totally exhaustive in the purest sense of the word?

No, I reassure you right away, it is a question of getting to the heart of the matter and answering the most pressing questions from parents and students by taking into account the most representative existing methods. Because, well, we're all very busy. We are not going to review all the new methods with nebulous foundations that only originate from their author's imagination.
It is a question of avoiding at all costs that the vast majority of students choose the wrong method, as well as the resulting additional costs of all kinds.

Is this analysis strictly scientific?

Of course not, and it must remain pleasant to read, but rest assured, it is still based on facts and elements, observable, real, and presented as and when needed for demonstration purposes.
I dare not imagine the work required to set up serious guidance experiments conducted by psychological researchers, with controllable variables and follow-up over 20 years or more, on a sufficiently representative sample of students. This is probably impossible otherwise I suppose that all the experts in state research centers on these issues, of which I am not a part of, would have published a guide for the public based on these questions a long time ago.

But then, what can you expect in this book?

A fine analysis of guidance methods, their limits and their interest so that you stop being fooled by the guidance industry, concentrating on the essential, because you have understood it, having myself a lot of hobbies, I am very anxious not to waste anyone's time.

If you think it could be interesting, buy it, read it and if you find that I wasted your time ask me for a refund, satisfying my customers is for me a matter of principle and that's what has kept me in business for the last 15 years.