To be honest, for the first 10 minutes of this film, you will probably be laughing at the ridiculousness. You are catapulted straight into the action without any introduction of characters, plot or surroundings. This film is violent, sure, but as I always say, it's how a movie is done that makes the difference. Shoot 'Em Up proceeds from one dazzlingly outrageous scene to another with unflagging confidence, tons of panache, brilliantly warped humor and blazing originality, sweeping you and many viewers along.
The casting is genius as well, beginning with Clive Owen, who's dead-on here, with his ever-present carrot in hand, rescuing the (adorable) baby, getting the girl, killing the bad guys (who just keep coming like deranged vampire replicants), even solving The Mystery from the most obscure of clues, all while complaining about everything he hates.
And speaking of the great Paul Giamatti, he's in monumentally fine form here as Hertz, the self-described brilliant leader of the gunmen. Squallid and seedy beyond all comprehension, you just know he's having a blast (pun intended) with this part. After proving in his last few outings that he can carry a film and play anything, he gets to bask hardily in full venal mode, sneering, scowling and torturing his way into our hearts as only Giamatti can.
The film is shot in stark, sharp tones, making it look like a comic book come to life more than any film I've ever seen, while still using real actors. And there are sequences here that you have NOT witnessed before, speaking of that originality I mentioned earlier. The one which stood out most to me is the one where Clive Owen and Monica Bellucci (also perfect) are making love and the baddies bust in. In most films, this would pre-empt the love-making. In Shoot 'Em Up, they continue the act, which actually culminates while the bullets are flying. Worked for me.