Could you do it? Could you give yourself to someone so completely that you trust them not only with your heart but your physical self beyond the bounds of traditional sexual engagement?
Crafting scenes like those experienced by Michael and Janine in the books has been among the greatest creative tests I have experienced as a writer. Imagining what it feels like to have your lover's hands gripped tightly around your throat...or the sensation of a flogger or belt against your skin while turning it into an erotic adventure that most readers can fantasize about without being repulsed. It's tricky, especially since most depictions seen or memories shared by readers about this type of sexual play are any thing but erotic.
I think that's the trick. Helping the reader enter a world with which they have limited to no familiarity and coming out of it a little more informed, less judgmental and maybe even turned on. Imagination is a powerful thing...sometimes it can lead us on journeys we never considered before.