I mentioned in my review of the first Quinn and Strange novel that you aren't supposed to really love Quinn and Strange, exactly. The detective novel requires you, on some level, to believe in the moral qualities of the detective so they aren't just a busybody. Strange fulfills that purpose in the first novel; Quinn, even right at the end, we are not supposed to fully think he's great.  In this, the second book of the series, this approach bears fruit.  Quinn still is who he is, and around the edges you still see that his views on race and violence still have a dark undercurrent to them.  Yet this time he is the one who receives acceptance and support, while Strange, who is a bit more of a judgmental figure, is genuinely challenged on his moral stances and actions.  Some he rises to.  On others he fails. 

About two thirds of the way through the book, Strange, who has been investigating the suitor of a friend's daughter as a favor, is confronted by that suitor after Strange uncovers a secret.  The suitor directly comes at Strange's moral judgment and turns it around on him. Both the reader and Strange are hit hard by it.  

The bad guys are given inner lives, and because our heroes struggle so much you start to truly understand the conflict between them.  This goes into my "best private eye novels of all time" list, with a bullet.  An incredible work.