The subject matter is definitely interesting and it's an important story to be told. It will leave you feeling that a great injustice has been done. The underlying true story is an example of how tribalism and the bias people show to those who look and act different from what we view as "normal" colors our perception of right and wrong and overrides what the facts show in this case to be cold blooded murder.
That being said the movie itself was a bit "meh." I'm actually surprised by the high ratings. It was a bit slow and boring. Put it this way: if it wasn't a true story I think most people would say the movie sucked. What makes it worth sitting through is the fact that it's a true story.