3.5 but may change to 4....
Although I do not like BDSM, in this book it is so light and well done I did not mind very much. Kael is a prince who is given as a concubine to the half-demon and half-brother of the Queen of another kingdom. Taren, the half-demon, is gentle and nice to Kael, although he also likes BDSM. Poor Kael (and his poor butt) becomes something of a boy toy. I could not help compare his life to a prisoner becoming his cellmate's boy toy. He becomes the "catamite" prince.
This kingdom is very sexual, but the story is not completely sex after sex, as the title and cover imply. It is actually very interesting (and I am not referring to the smutty scenes only). I was very into the story the whole time. Eventually we learn that SPOILER**Kael is Taren's mate, and that makes Taren AND Kael go all "mine" behavior.**
I liked that Kael was very manly and that in spite of his situation, he is never depressed. He embraces his role pretty quickly, thanks to Taren's skills, who "tames" Kael (I loved the similarity with the horse).
So this book has butt-plugs, harnesses, a bit of exhibitionism, pierced nipples, and in spite of all that, I loved it. Not too romantic (they don't even kiss until after half of the book, and when they do, they don't kiss as much as I wanted to... kisses are underrated in this book, sadly) but it is also not too dramatic.
New word I learned: catamite O_O