Strangely enough for so such an obvious device, this can sometimes allow the writer to show us some really big and powerful things, just by tweaking the perspective a little bit. Walter Mosely's “Easy Rawlins” mysteries are my favorite example. I love the old Raymond Chandler “Philip Marlowe” hard-boiled detective stories, the basis for “The Big Sleep” and other classic noir films. Easy Rawlins is a PI (unlicensed) in the same city as Marlowe and at close to the same time (the Marlowe stories start in the 30s, the Rawlins stories in the 40s) but Easy Rawlins is a black man, and that fact alone makes a huge, huge difference.
The Marlowe stories usually had some level of political commentary (along with some gratuitous homophobia and racism) but the Rawlins stories are largely about the issues of race and class in American history, told through the medium of crime fiction so compelling and readable that it's never taken me more than about two days to read any book in the series. Rawlins, in a way, is a take-off on the Marlowe archetype- but the Rawlins stories are actually better. Not exactly because they're more political, and certainly not because they're “politically correct.” These things are irrelevant to whether a particular story is told well or poorly. The Marlowe books are less political, but they are also classics in their own right. The Rawlins stories are superior because the author uses his political perspective to get to some huge and very moving truths, and that makes them more powerful as stories.
I haven't said anything about this movie yet, but I'll tell you this- the movie of “Devil In A Blue Dress” is what got me into the books. I've already seen it about ten times, and I'll probably see it ten more. How's that for a review?