I'm afraid I put down Farley's book after the second chapter. Too much theory and talk about justice. I liked the work she did on cultural viewpoints, but once she got to Christianity, it all devolved into concepts and theories too much for my taste.
In my opinion, the point of departure for a theology of human sexuality is the simple statement that we are sexual beings whose self-realization is necessarily tied to our sexual expression. Sometimes that means being chaste. Sometimes it means giving your boyfriend a little hand relief during Harry Potter reruns. But none of it is intrinsically bad and most of it is intrinsically good unless it exploits us or our partners. Most importantly, there is not a God out there somewhere getting all bent out of shape because someone's wife got a vibrator for Mother's Day. 
Sorry if that offends, but no one has sex by concept. Sex necessarily has to do with rubbing something or someone, and if we're not willing to talk about that, we're full of ...