In this story, the main antagonists lived underground mostly a few above as servants. Another main character was a half breed of that race and human.
I read this years ago from 2014. The bad guys lived underground. The good guy was the inspector who had all his nerve impulses changed through gene manipulation, such as changing sweating when lying to instead cause his hands to turn cold. The main "good" female was a half breed between the two races and had a female servant of the antagonist race.