What really kept my attention for me despite an unlikable narrator was the chemistry between him and Dante. Definitely some steamy scenes and tension galore.
Dante is your intriguing, dark and handsome alpha-male with a vulnerable side. However, I felt his transformation from a promiscuous and self-declared cold-hearted bastard to someone ready to settle down into a committed, monogamous relationship after declarations of love to his 'dear' happened waaaaay too quick. Again, I reminded myself to just take it in stride, as I did with the rest of the book, so it didn't bother me too much in the end. As much as I like happy endings, I do find it hard to believe someone like Dante will stay faithful for long, but I believe that they can weather through it. Zack is clearly a pushover when it comes to Dante.
I don't have much to say on the crime/multiple murders aspect, but though the murderer was obvious to me at least, it still maintained my interest through the end. Zack's repeated screw-up decisions as a supposedly seasoned detective prevented me from enjoying the case too much.
That said, it seems like I listed a lot of issues I had with this, but strangely, I found myself enjoying it, hence 3.5 rounded up to 4 stars. It seems that Scarlet Blackwell's books tend to have mixed reactions among readers, but I am a fan and her books have always been a guilty pleasure for me.