DNF. I usually try to make it 50% into a book before quitting, but I just couldn't. Was it the menage? No (I didn't actually get to the menage, but I went into this book knowing that the relationship is M/M/M). Was it the plot? No.
What I couldn't tolerate was the characterization. There are three characters: Yarrow, the mage that shares his body with an evil entity; Duncan, the knight who is loyal; Sasha, the assassin that denounced the ability to love. All characters felt flat and, quite frankly, annoyed me. It's like the author wanted to make three complex characters, but ended up quite the opposite.
Yarrow, who appeared cold and apathetic at first, is really annoying. For example, He sleeps with Sasha, hates it when Duncan calls him a slut, then goes and has angry sex with Sasha afterwards. What? Then there's Sasha, who says he can't love. But develops insta-love with Yarrow, and develops quick feelings for Duncan. Okay...? And Duncan is all loud and proud of his hate for the assassin, yet quickly changes his tune. My favorite character was the evil entity inside of Yarrow. At least I got some humor from it.
The writing felt a bit bland, which was impaired by the head hopping POV we get between the three characters. Overall, this fiction just didn't work for me.
Edit: Cleared my rating from 1 star. I figured it wasn't fair to rate the book since I didn't even reach 50%.