"Joan and Kip Sewell knew before they got married that he liked having sex more often than she did. But it wasn't until they had wed that the extreme nature of the disparity became clear: he wanted it nearly daily; she wanted it nearly never. Even when the sex was good, Joan could take her orgasms or leave them; sex for Kip, on the other hand, was as physically ecstatic as it was emotionally important. Obviously, to save their otherwise healthy marriage,...