Everyone knows who J. Robert Oppenheimer was, so I'll skip the background.
Think of this movie as much about the Manhattan Project as The Imitation Game was about the Bletchley Park Codebreakers. Like the Imitation Game, while the setting is huge and historic, it's really a story about an individual. In the case of The Imitation Game, it was about Alan Turing, the immeasurable contribution he made to the Allies winning WWII and the shameful treatment he received afterwards from the very government that he worked for. In Oppenheimer, it is about J. Robert Oppenheimer, the immeasurable contribution he made to the US winning WWII and the shameful treatment he received afterwards from the very government that he worked for.
3 hours long, the movie bounces back and forth through his life, covers the creation and success of the Manhattan Project and the subsequent treatment by the government, in particular the McCarthy communist witch trials and the glory-seeking politicians involved. Oppenheimer was, by all counts, a genius, somewhat liberal and very sympathetic to the working people. He was also a bit of a womanizer who was more than happy to travel in communist circles if it meant getting laid. His wife, in fact, was a card-carrying communist in her younger days. But what really got him in trouble was the political naivete when it came to scientific endeavor.
As a scientist, he wanted as much collaboration as possible, even if it included the Russians, who were our allies at the time, but socialist and therefore, the enemies of our enemies, but not our friends. His downfall comes when he strives to stop the arms race from starting by opposing the development of the hydrogen bomb while the Military Industrial Complex and the politicians wanted bigger and better things that go bang. The movie does a great job of walking us all through the trials and tribulations of a first generation American born of German Jews navigating his way through the world of physics.
Fun: Not so much fun as very riveting. Unless you count the gratuitous appearance of Florence Pugh's breasts, which are lovely.
Preachy: A bit of anti-government flair, mixed with a hint of pro-communism and blasting of the McCarthy-era congressional circus, most of which is completely justified by history.
