I have read some extracts from this and ordered the book; it looks like a very interesting read.
I'll update after I've read it, but my feeling is that I'm going to agree with some bits and disagree with others.
From the overviews and extracts I've looked at, it looks as though the book could have benefited from more cross-historical and cross-geographical comparisons. For example, out in East Asia where I live, some countries have generalized use of the birth control pill and abortion, and some haven't, or one of the other, or the timing was different. Yet ideas about family formation and rates of out-of-wedlock births have remained very very conservative, regardless of these differences. I'm not sure the pill makes the big differences she suggests. Abortion, similar. Meanwhile, in much of Latin America, there was a big move towards looser unions and high rates of out-of-wedlock births quite a while back, while widespread access to things like the Pill and legal abortion happened a lot later and has been quite recent. Stuff like that. As far as I can see, the only rule is that "Culture eats everything else for breakfast, and everything is downstream of culture."
My experience of living in a society (Japan) where marital norms are very conservative, is that there are upsides and downsides, and also things that remain very much the same.
It hasn't done anything to stop porn and prostitution culture here, for example, (and prostitution was arguably commoner before the sexual revolution in most countries, including Japan--in Victorian London, around half of men regularly used prostitutes, as opposed to about 10% today).
A very conservative culture about marital norms in places like Japan and China and South Koreayou must NOT have babies out of wedlock, if you're miserable in your marriage you just informally separate and don't live together or have sex together again, you won't be allowed to become a single mother by choice via sperm donationhas some benefits, as it means fewer children are exposed to the risks and upheavals of stepfathers/mum's boyfriends, blended family drama and the like.
But it also means fewer children get born in the first place, as premaritally conceived kids get aborted rather than born, and people just informally separate from hated spouses rather than divorcing and remarrying and perhaps cementing that union with an additional child. Most demographers agree that in developed countries, more conservative norms around childbearing correlate closely with low fertility rates. And that issue will also destabilize society in other ways, long term. For people like LP, who are pronatalist, this means that some difficult conversations about trade-offs will need to be had. These conservative norms also deprive many women of the joy of having a child that they might have loved very much. I should not need to add, that these norms also result in some cruel stigmatization and mean-spirited, narrow-minded treatment of any family who falls outside these norms.
I just mentioned abortion; LP seems to treat the Pill and abortion as part of the same package, but that's not the case universally. Generally, people shift towards small families as societies modernize, regardless of whether they have the Pill (it's still very rarely used in Japan, for instance; it only became common in the old Soviet bloc decades after these women had started having very small families). What the Pill does seem to do is reduce the need for abortion, because it has a lower failure rate than most other methods. So again, hard conversations about trade-offs will need to be had, for those who aren't keen on the birth control pill.
Sorry for long and rambling post. Just posting some initial thoughts here.