It is a movie about something that is probably important regarding the fact that NFL players in USA are subjected to basically a car-crash scenario that completely mucks up their brains - and the people involved in exposing this are real (big win!)
Will Smith pulls of a convincing Nigerian accent as he plays the role of Dr. Bennet Omalu, who is a real person that first revealed what we now know as obvious information; the fact that pro sport people can not be hit in the head at full speed by another giant person over and over again without long-lasting repercussions.
The film is good, in that it deals with something that actually happened and involves the real names of at least some of the people that are involved. Dr. Bennet Omalu is an immigrant who stumbles upon the fact that recurring head injuries to NFL football players actually has a lasting effect on them in their lives and well, the NFL doesn't want this to be public knowledge.
The movie is kept moving as best they can by the things that one would expect to encounter when trying to take on the most popular sport in the United States in what appears to be (at least at first) an attempt to shut down the entire operation. Considering the absolutely massive amounts of money involved in professional sports in general, this is easy to understand. If you are an NFL fan (and I am) you have probably noticed a bunch of new rules that have been introduced as far as contact with the head is concerned - This film tells you why that is happening.
The movie might be interesting to a certain demographic but mostly I don't feel as though there was enough actual material (real or made up ) to make an entire film here. I was bored for a lot of it and as it turns out a great deal of the "fun" stuff in the film is actually just entertainment fiction that was made up so that they could have a whole film here. The underlying message is real, but many of the names were changed presumably to avoid massive lawsuits which the film kinda hints at while it is going on.
Overall, I think this movie might be interesting to an American audience, but not so much for the rest of the world. This is reflected in the probably-not-breaking-even-after-expenses box office count.