There are three elements that make this quite brilliant.
While the actions of mail bomb murderer, Ted Kaczynski were reprehensible, his ruminations on evolving technology, and the dangers it necessarily posed to mankind were prescient and largely proven right by the relentless advance of social media. It is fascinating to visit Ted's predictions with twenty years of hindsight.
Paul Bettany as Ted, is utterly brilliant.
The science of literary or linguistic forensics was developed to capture the Unabomber, and ultimately led to his identification and capture. We get a "TV" eye on this that is nonetheless, interesting and informative.