Grain of salt here because it's been a hot minute since I read it. IIRC, He's allowed to have sex with his wife and only his wife, and his wife and him hate each other. He wants to have lots of casual sex but that's only allowed among the party members. He laments that the party members won't sleep with him and that all the women he'd like to sleep with are untrustworthy and will snitch him out. His wife ends up leaving and he meets the nympho and they start meeting up for sex. That's what I remember