Breach
I enjoy movies based on real-life events because of the post-movie Google/Wikipedia binge. You start at the Wikipedia page for the movie in question and work your way out from there. In this case, I read about convicted spy Robert Hanssen and the agent who helped catch him, Eric O'Neill, who has his own web site and a wife who's prettier than the actress who plays her in the film, surely a rarity. The most interesting aspect of such research is the differences between the real-life events and the filmed narrative. It's fun to think about why those changes were made and how it made the narrative better or worse.