You could boil this book down to one key action item for straight men: Always insist on wearing a condom, even if the woman doesn't want you to. (Unless you're actually trying to have a kid, obviously.)
The case for this is simple. Pregnancy imposes much larger sacrifices on the mother than on the father. At the same time, men's options for preventing pregnancy are far less burdensome than women's options. Blair details the hassle involved in getting birth control pills and the litany of side effects that go along with them; the hopeless inaccuracy of any attempt to predict when a woman will be ovulating or not; the intense pain often associated with insertion of an IUD; etc. The contrast with condoms, which are cheap and painless and have the added benefit of helping protect against STDs, is stark.
Men also have better surgical options than women. I remember learning as a kid that tubal ligations are much more serious procedures than vasectomies, so I was shocked to learn from this book that they are nevertheless more common ("27 percent of women who are sexually active get tubal ligations"). I was also unaware of how reversible vasectomies are:
Successful reversal rates are known to hover around 75 percent for vasectomies reversed within three years, with less success as the time between vasectomy and reversal attempt increased, but happily, things are improving. The Stanford Medical Center reports that, depending on the type of technique used, their vasectomy reversal success rate is 95 percent and makes clear that the length of time between the vasectomy and the reversal doesn't affect that success. The International Center for Vasectomy Reversal in Arizona, says, "Our experts can achieve a proven, published success as high as 99.5%."
Blair hopes someday reversal procedures will be good enough that it could become normal for men to "get a vasectomy when they are ready to be sexually active and then reliably reverse it if they and their partner want to conceive" but acknowledges we aren't there yet.
I think Blair makes a very convincing argument that men should proactively choose to wear condoms even if the woman does not bring it up - or even if she says she is OK with unprotected sex - because there is significant risk that she's acting out of fear:
The reality women face is that if they say no to sex, or no to unprotected sex, the man may respond with violence and anger. This may be a difficult thing to imagine if you don't regularly go to bed with people who weigh twice as much as you do and can easily break your neck. ... Women may be emotionally rejected, they could be verbally assaulted or kicked out of their home with nowhere else to go, they could be hit or choked or otherwise physically assaulted, they could be raped. This anger could come from a man they don't know very well, but it is much more likely to come from a boyfriend, husband, or other established relationship.
Blair takes this a bit further though. She seems to think that even if a woman explicitly requests and prefers unprotected sex, the man ought to refuse; and if he doesn't, any unwanted pregnancy should be viewed as primarily his fault. "Men cause all unwanted pregnancies", Blair insists. She realizes her male readers will be skeptical of such a strong statement, and tries to anticipate and respond to objections, but I still think it's an overly extreme claim. Perhaps the root of our disagreement is that she seems to believe it's objectively bad to risk pregnancy if you don't want a child; she says "[a] woman suggesting sex without a condom is acting irresponsibly", and even implies at one point that it's "essentially self-harm". If you accept that, then this analogy she gives makes sense:
...consider two buddies making a video for TikTok. They have a gun, and Buddy #1 says, "Shoot me and let's film it." Buddy #2 says, "No way." Buddy #1 begs, "Come on man, it will be so cool, we'll go viral." Buddy #2 still refuses. He won't do it. Buddy #1 keeps pressuring, "Dude, just do it. If anything bad happens, it's on me; it's my idea." Buddy #2 is persuaded and decides to shoot Buddy #1. Buddy #2 pulls the trigger. His intention was just to wound Buddy #1, but his aim slips and the gunshot is fatal. Buddy #2 is convicted of manslaughter and goes to prison.
The reason we should condemn Buddy #2's actions, I think, is that taking a bullet for a TikTok stunt is such unreasonable behavior that nobody should be allowed to consent to it. Is having unprotected sex when you don't want a baby so unreasonable that nobody should be allowed to consent to it? People vary a lot in terms of how much they value various experiences and how much risk they're willing to tolerate in order to have those experiences. I think we should be very hesitant in overruling another person's judgment about whether any given risk (to themselves) is worth taking. Even in the TikTok example, assuming Buddy #1 is an adult and has taken time to carefully consider whether he really wants to do this, I'm only hesitantly persuaded that we should disregard his desire and forbid him from taking the risk. A desire for unprotected sex seems less extreme (particularly for women who see abortion as an acceptable fallback plan). So if a woman who understands the risks genuinely prefers unprotected sex, then despite Blair's arguments it still seems to me that responsibility for any resulting unwanted pregnancy should be attributed equally to both consenting parties.
I don't think this affects the practical conclusions of the book much, though. Because of the risks women face if no form of birth control is used, the major advantages of condoms over other birth control methods, and the power dynamics that discourage women from asking men to use condoms, it would be beneficial to establish a strong social norm that men must always wear condoms by default, and that deviating from that default is a very serious decision.
I think every teenage boy should read this book or something like it. Even reading it now in my 30s I learned an embarrassing amount from it. (You will not be surprised to hear that the conservative Christian school curricula I was educated with was not hugely informative on the subject of women's reproductive health.)
But what about the book's subtitle, "A Whole New Way to Think About Abortion"? Blair aspires "to shift the conversation away from the usual for-or-against debates that have stymied this issue for decades." Will this work? I'm not optimistic. She wouldn't just need to convince people that holding men accountable for impregnation is the most effective way to reduce abortions and unwanted pregnancies. She'd need to convince a large number of either pro-choicers or pro-lifers that holding men accountable is so effective that it's worth ceding control of abortion law to the other side in order to focus on it. Suppose it could cut the number of abortions sought in the US per year by 99%, from about 930,000 to 9300. Would my fellow pro-choicers and I stop demanding abortion rights if only 9300 women would miss them? Or would pro-lifers let go of their outrage about the government tolerating what they believe to be murder if it would only happen 9300 times? I'm guessing the answer for both groups is "no" and that we'd still be stuck fighting bitterly about whether abortion should be legal, even if we all agreed that legality is only a minor factor in determining how many abortions are sought or performed.
Regardless, it would be a very valuable point of agreement. While the fight over whether abortion should be legal rages on, both sides could at least work together on reducing the number of people whose lives will be affected by the outcome of that battle. But will pro-lifers find this appealing? Many are very invested in discouraging extramarital sex regardless of whether it results in unwanted pregnancy, because they believe it has been forbidden by God. This means that the kinds of accountability they're willing to encourage for men are the kinds that don't work well: just telling men not to have sex, and ratcheting up the shame and guilt on men who do. They're reluctant to educate men to use condoms consistently or be more open to vasectomies, because it feels like making it easier for men to do something inherently bad.
Hopefully I'm being too pessimistic. The author reports seeing people change their minds as she's discussed her ideas with them. At least one friend of mine also reports success in getting pro-lifers to reevaluate their views in light of the inefficacy of abortion bans.