A bit of both, I would imagine. I know for the whole, pure fantasy thing, that giving up all control can be very attractive, and the whole negotiation thing can be a drag. It can also be interesting. I mean, The Story of O doesn't exactly cover negotiating a scene and proper use of safe words, nor do any of Rice's Sleeping Beauty books. But, I've read a few that seemed to be trying to do a realistic job of portraying kink, and o holy fuck me somebody's gonna get hurt if they take this seriously.

On the other hand, the is a rather good Vigorli story with Orli as the top, that not only covers negotiation, but addresses ways things can go wrong when you don't communicate well, and often. "Boundaries" by lostiawen. Everybody who wants to write kink should read it.