As an Atlantan who thought I had a good grasp of local history, this book was a splash of cold water in the face. Very informative. 
 Two rookie black officers must investigate a murder case that the whites don't care about, or worse, are covering up. In the first few chapters, Darktown reminded me of other police procedurals where the clean/honest cops (in this case, the black rookies) have to investigate around the dirty cops (here, the ultra-segregationists on the police force). But the further the story develops, the clearer it becomes how severely the deck is stacked against the black officers. They are dealing not just with discrimination in the police force, but when they're off-duty as well, which complicates their unofficial investigation even further. 
 The book vividly illustrates the effect of segregation on the black community in Atlanta and rural Georgia in the 1940s. Highly recommended.