Lowen writes both about what sex can be at best, and what it usually is in fact. Most other writers on sex can only do one or the other. Lowen also bridges here the biological and the psychological as he does in his other works--another rare achievement. Sex is not everything, but it is fundamental. Understanding sex is fundamental to understanding human functioning and human suffering.
Two things should be gotten out of the way: 1) Lowen considers homosexuality a far less than optimal sexual expression. This is not saying too much, because in the context of the Wilhelm Reich and Alexander Lowen tradition, about 99% of people are considered to have less than optimal sexual expression (including Lowen admits, himself) Still he writes about the subject with a slight flavor of condescension. 2) Lowen seeks to explain commercial sex work in purely psychological terms. Perhaps because, unlike the entire rest of his writing, he did not speak from his vast clinical experience, this section seems to fall short of his usual great explanatory skill.
This book is likely to be upsetting because it bursts many illusions about sex. Sexual functioning has not gotten any more satisfying for most people since this book was written, probably it is generally less-satisfying, because estrangement from the self, from the body, and from feeling has gotten worse in those five decades.