At Her Command - Marcia James I thoroughly enjoyed this romantic suspense. The mystery was there along with some hot sex, a few laughs and some sex toy education.

Domino is a DEA agent that goes undercover at a dominatrix club as Mistress Bella, to uncover a drug ring. One of her first clients is Dalton who is a local cop, posing as a client to find the killer of his partner and best friend, who also was undercover at the club before his murder. There are sparks from the very first meeting between these two but Domino isn't sure she could be with a man that wants to be submissive (no matter how difficult it seems for his alpha-male self) and Dalton isn't sure he could be with someone that wants him to be submissive.
Throw in an undercover FBI agent, another undercover female cop, who also have great chemistry and a tiny, drug-sniffing dog and you have a fun story.
I hope she comes out with a sequel as it seems to be set up for one.