Full disclosure: I read this book before it was released; I had access to a digital copy of the galleys.
This book should be read by anyone who has been exposed to the “debate” about gender-affirming care, which in the past few years has became a bizarre obsession of news publications, a handful of self-described "journalists" who profit handsomely from feeding a moral panic, and right wing politicians whose agenda is to demonize LGTBQ people and legislate against their very existence.
Dr. Turban systematically and calmly clears up the picture. He acknowledges that a lot of research remains to be done about how to help transgender and gender expansive teenagers, as we don't have all the answers yet —but that is also true of many other areas of science and medicine.
However, what matters is the big picture: All research we have so far, no matter how limited or "low quality" (a technical term that Dr. Turban explains in the book, as it doesn't mean that existing evidence is "bad") points in a similar direction: the current model of gender-affirming care, if applied cautiously and in a collaboration between teenagers, their parents, and their healthcare providers, usually leads to positive psychological outcomes in a large majority of cases.
More importantly, "treatments" that critics of the gender-affirming care model propose as alternatives—"gender-exploratory therapy", for instance, akin to conversion therapies that have been used against gay people for ages—have no evidence whatsoever to back them up, and some have been shown to be harmful.
There's no legitimate "debate" about these two core facts, at least until new evidence refutes the first or corroborates alternative models, something that I believe is very unlikely. The true debate is on how to improve the current model and for that, much more research is needed. Science is always a work in progress.