When you get a bunch of unknowns, a few stars, a standard heist plot, and a director who has something to prove, often you get movie magic. Reservoir Dogs. Usual Suspects. The Town. Den of Thieves is none of these movies, but it gave it a hell of a lot of effort and that's worth something.
Cops and robbers are set against each other. The robbers are out to steal all the money from the Federal Reserve. The cops want to scare or shoot them or have sex with the robbers. I can never tell, but the movie takes the time to show how sad Gerard Butler's life is and how awesome it is to have a robber crew.
Why is that? Most movies with cops and robbers, the cops suffer on the regular while the robbers drink and have fun. I think it's the bureaucracy. Paperwork just kills you, man.
Let's point out the real reasons to see this movie: Gerard Butler is channeling manic-Denzel from Training-Day and the action/heist is super fun to watch. Butler pops his eyes, drinks, and posits the relationship between good and evil. Then he makes the guy his soon to be ex-wife is hanging out with hug him and it's just madness. The shootouts after the failed heists equal that mania with sprinting gunmen and pounding folley work. The bullets fire like drums in the city jungle of Los Angeles, making this roaring movie electric when it gets where it needs to go.