I’ve always been a big believer in the common-sense obviousness that monogamy is hard. Additionally, I like the idea of my wife getting fucked. I don’t have any desire to be denigrated or emasculated; I just get off on the idea of her being satisfied and a little transgressive. Early in our relationship, we talked about monogomish guidelines: I’d like to be informed and consulted, and she would rather I kept mine to myself. Last weekend we were having sex, and she asked me if I “wanted to hear a story,” code for treating me to a tale of a sexual contact. She’d been out of town for work most of the summer, and she told me that one of her roommates had gotten in the shower with her and fingered her until she came. I asked her if she’d fucked him, and she said yes. It was all hot and awesome. But a...