The Queen (The Original Sinners #8) by Tiffany Reisz

Once upon a time, Nora and Søren made a fateful deal—if he gave her everything, she would give him forever.

The time has finally come to keep their promises.

Out of money and out of options after her year-long exile, Eleanor Schreiber agrees to join forces with Kingsley Edge, the king of kink. After her first taste of power as a Dominant, Eleanor buries her old submissive self and transforms into Mistress Nora, the Red Queen. With the help of a mysterious young man with a job even more illicit than her own, Nora squares off against a cunning rival in her quest to become the most respected, the most feared Dominatrix in the Underground.