Under and Alone by William Queen
I just finished "Under and Alone" and was really blown away. I’ve only met one undercover detective before, but he struck me as an odd guy. I met him at the trial of the operators of the Centreville poker game I used to play at. He really didn’t have to worry that much about getting killed if discovered.
Queen, on the other hand, ran the risk every day. The brothers in the gang out and out told him so, and more than once a violent drunk biker brethren threatened him to see if they could get him to crack. The crimes the Mongols were involved in, and the viciousness they used routinely were appalling. There’s nothing romantic about this underworld, and I’m glad I know more about it. I’d never want to be in the same room as any of these guys.
It’s a quick, pulpy enjoyable read, and I encourage you to pick it up.