This book is the work primarily of Sheila Gregoire (along with Rebecca Gregoire Lindenbach and Joanna Sawatsky), and it comes out of some large scale research they did, surveying over 20,000 women in (as I understand) relatively conservative Christian contexts, about sex, marriage, and their beliefs about sex and marriage. That, and the qualitative interview work that followed, produced this book, whose basic premise can be summed up like this: there are a number of common evangelical beliefs about sex and marriage that are at least correlated, but in many cases causative, of harming marriage and sex lives (overwhelmingly but not exclusively for women; they surveyed women, they are mostly interested in women, partly because, as they say, women are the people with worse outcomes in this area). For Gregoire, as she puts it in the introduction, Sex should be : personal, pleasurable, pure, prioritized, pressure-free, put the other first, and passionate.
I won't attempt to tackle all the book's content, but I will highlight some of the beliefs they highlight. I find it interesting to consider that even when a woman stated that they didn't believe a certain proposition, if it was consistently taught/prevalent in their church/Christian context, it would still correlate to negative outcomes.
Gregoire tackles head-on prevalent ideas that women have emotional needs, men have sexual ones; that men need sexual release and women do not; that women have obligations to sexually service their husbands, etc etc.. All of these correlate to reduced sexual satisfaction in women, and to unhappier marriages.
Chapter 5 is particularly important, in several dimensions. It tackles the prevalent teaching that all men struggle with lust, that men are visually stimulated, must avoid looking at women, and women must cover up. Gregoire et al make several arguments. Firstly, they helpfully and rightfully distinguish between lust and sexual attraction. Sexual attraction is a natural response to stimuli, lust is an intentional desire to have sex with someone. And again, "it is one thing to say, for most men, sexual arousal results primarily from visual stimulation, and quite another to say, for all men, lustful thoughts will happen unless he avoids any visual stimulation" [82]. The first is true (i.e. psychological research supports it), the second does not follow and is harmful. The effects of this belief are, for men : living in a constant state of anxiety around interacting with women; for women : harming their view of men by portraying all men as lustful, untrustworthy, predatory beasts. This belief has this effect (though not as strongly) even when women don't believe it, but are consistently exposed to it. Each chapter has a section at the end headed "Rescuing and Reframing", designed to take common thoughts/statements and present better alternatives. Here they suggest the path forward is to recognise that lust and visual stimulation are problems for all kinds of people, not just men; that we all have a responsibility to treat other people as people, with respect and integrity, regardless of sex and gender. This shouldn't be rocket science....
Reading books like this sometimes makes me glad that I didn't grow up really on the inside of a church or Christian culture. There would have been many beneficial things about that being true, but as much as I recognise many of the teachings in this book, I don't recall actively encountering them in a lot of contexts. I would say, at least in the church circles I move in, there is very rarely topical teaching on sex in public contexts. That kind of teaching is more likely to take place in single-sex conventions, and through books; but as the authors of this book point out, (very) many of the best-selling books in this field contain considerable material that is harmful (and just untrue).
There are chapters that also tackled sexless marriages, and the significant harm of teaching that women should give sex to men as a duty, or the even more horrific reality of coercion and marital rape. There is a terrible banality to evil, and it's horrifically unsurprising that patriarchal visions of reality enable and condone marriages where women's consent and bodies are violated. These things should not be.
Overall I think this is a very necessary book, and one that ought to be more widely read. A large proportion of Gregoire's readers are women, but I think this book should be read by a lot more men; I also would recommend it to single people, because (i) recognising and combatting harmful lies about sex and marriage is a good thing before one gets married and (ii) even if one does not get married one should gain a healthier framework for understanding sex and marriage, and so its a broader shift of (sub-)cultural teachings that needs to take place within Christian churches.