Well, actually the book is called Has Marriage for Love Failed? but it has this utterly epic book description:
Today we like to think that marriage is a free choice based on love: that we freely choose whom to marry and that we do so, not so much for survival or social advantage, but for love. The invention of marriage for love inverted the old relationship between love and marriage. In the past, marriage was sacred, and love, if it existed at all, was a consequence of marriage; today, love is sacred and marriage is secondary. But now marriage appears to be becoming increasingly superfluous. For the past forty years or so, the number of weddings has been declining, the number of divorces exploding and the number of unmarried individuals and couples growing, while single-parent families are becoming more numerous. Love has triumphed over marriage but now it is destroying it from inside. So has the ideal of marriage for love failed, and has love finally been liberated from the shackles of marriage?
So, I mean, first of all, I just totally love that apparently this author has basically never done ANY HISTORY AT ALL except in-depth studies of a fantastical conservative paradise -- possibly taking place in an alternate universe 1950's? Because I see you your conservative wet dream about how marriages totes worked and raise you the entire history of marriage. Or if that's too much research for you, just go read A Distant Mirror and the chapters on chivalric love and how the "ideal" love was between a knight and a married lady who wasn't his wife.
But beyond the haha-hilarity level of this, I find it frankly offensively hetero-normative to idly wonder if love has destroyed marriage in a time when there are numerous places on this planet where many LBGT people are still not allowed to marry the people they love, and where legal battles are being fought on a near-constant basis to allow them to marry their loved ones.
Love and marriage and whether these things are right for us, individually, is not an equal question to be mused on by all people. What is a thought-experiment for the privileged is the painful oppression of the marginalized. And I would suggest that before writing a book about marriage, it might be a good idea to step outside one's own privilege-bubble and understand what marriage meant in the past and what it means in the present for people less privileged than you.
Just a thought.