Not a racist movie, there aren't afro-americans (it's set in London), the white guy in the gang is not scared, in few words the movie is exactly the opposite of what the troll (or dumb) Jake Osborne wrote in his completely meaningless review.
Plot is quite linear and simple, but this movie keeps on being interesting from first to last frame, there are no holes or boring parts, and the mix comedy/horror sci-fi is well balanced. There are no flamboyant special FX, but you don't miss them because action is the real engine behind tension.