Falling for Dad's Slut

Evan, twenty-one, falls in love with Stella, twenty-four, a girl/boy/man who he finds in the company of his playboy father. Evan knows right away Stella is a slut.  And not just any kind of slut, she's a slut of the most debauched kind, the kind that chases cock with abandon. The story is ninety percent sex.  Wild, kinky, endless sex.  Exhibitionism is a major theme: the characters flash and have sex in full view of strangers again and again.
 Propriety is their least concern -- they like it messy and dirty.  They engage in uncertain gender role play and tongue-in-cheek power dynamic play. For Stella, it's all about having fun. For Evan, it's finding love and meaning.  He would like nothing more than to have her as his girlfriend, and he does his best to get her. He likes Stella for what she is, yet it's exactly her -- their -- nature that makes connection difficult.
 Evan is an engineer.  He solves problems, he does not talk or analyze feelings.  Stella does not belong, and does not care to.