Billy spent much time training Tanny to like pain -- or trying to. From what I understand, that's how it works. Billy kept biting Tanny, and Tanny kept saying that he didn't like it, and thinking that it was weird. Billy believed that "Tanny's body said he liked it," no matter what Tanny said verbally. The BDSM was all about what Billy wanted, and I thought it should have been more about what Tanny wanted.
Billy left Tanny in handcuffs for the better part of two days -- an evening, overnight, and then into the next day. I didn't like that too much, either. Billy gave Tanny a whole bunch of toys for Christmas, for Billy to use. Tanny didn't even know what most of them were.
The power dynamic was a bit screwy, too, in that Tanny had been homeless, and it felt kind of like it would be hard for a formerly homeless man to refuse a man who had given him a home. It was clear that Tanny would say he didn't like something. It was just that Billy thought Tanny either actually liked it or would learn to like it.
I liked Tanny, and I liked Billy outside the BDSM scenes. Since a good part of the focus of the book was on the BDSM scenes, there were frequent enough times that I wasn't liking what Billy was doing.
It's not that I can't like books with BDSM. I've posted before about books I liked that had it, including Syd McGinley's Dr. Fell books. It's just that I never believed that Tanny liked the pain.