Interesting review of a new book - by a Marxist academic, but according the review "laugh out loud funny" (in a good way).
It strikes me that in a book about relationships and marriage, that ignoring, the admittedly small, polyamory movement is somewhat surprising, but not unexpected.
Myself, I'm pretty in tune with the cultural norm of a single monagamous relationship, but given how many of my friends are both very intelligent and also in complex polyamorous relationships, I do think it is a subject worth some attention in a book about love and marriage... since adultery is somewhat different in a polyamorous relationship (though, I think if I understand things correctly not impossible - it would be a relationship that is kept from the other person or persons in the relationship).
In any case it sounds like a book worth a look, though with the dual caveats of being written by a Marxist and seemingly ignoring the option of polygamy (i.e. a relationship with multiple consenting parties, often long term).