PPs (police procedurals) are a staple of the film/TV industry and are (believe it or not) as common as comedies or romcoms. However, within that category, "big" PPs based on big crimes are not that common. In fact, you would have to go back to the early 70s when a number of "big PPs" like Day of the Jackal 1973 were all the rage.
So, a film like this done properly (and, trust me, this one is done perfectly) would be a treat all by itself. However, what makes this film extra-special is the extensive use of video footage.
Now, to be clear, video footage as a plot device is not new by itself. It is now, and has been used extensively in British film and TV because, as we all know, London is the most "surveyed" city on the planet.
But -- the point -- nothing the Brits have ever done with the forensic use of video comes even close to what Berg brings us in this excellent film. Much the same way that the original creators of CSI-Vegas introduced an entirely new sort of sub-genre, it can be argued that Patriots Day similarly has taken the police procedural to an entirely new level.
The film itself? Brilliant! Berg has taken a stellar group of A-listers and make them work as a team, mirroring on the subliminal level the theme of the movie, which is both positive, and hopeful, and suggests that if we all work together, we can accomplish pretty much anything.