I saw the show on Broadway.
It's about the way that people look at different types of relationships if one wanted to get philosophical about it.
It's really about a married man, with a son, who falls in love, and sleeps with, a Goat. We get to see the reaction of his friends and family when they find out and his justification of the act to them.
"Smart! And into all those exotic mystiques -- The Kama Sutra and Chinese techniques. I hear she knows more than seventy-five. Call me tomorrow if you're still alive!"