In a world where it can be tricky for nonmonogamous people to find each other, or find enough of each other, and where some people figure out their nonmonogamous nature while already in relationships, it’s natural that sometimes, nonmonogamous and monogamous individuals end up in intimate connection with one another. The results, “mono-poly relationships,” are the subject of extensive discourse, to the point of getting an entire chapter to themselves in More Than Two Second Edition. And...