This is a film described as a 'comic thriller'. I can tell you it is neither. This is honestly one of the worst films I have ever seen and I can now understand why I'd never heard of it until I was browsing through the Sky Movies channels last week.
The plot is poor, as it depressing and doesn't compensate this with humour or an interesting story, more one of desperation and weird characters. I know if every character was normal, a lot of films would be boring but they weren't weird in any good way.
Oh, and the ending is the worst bit. Everybody dies including the main character. If it's a dark comedy like this is supposed to be, then the bad ending should be more funny, like Big Nothing where 'The Eye' kills Simon Pegg because he called him fat. But this ending isn't humorous in any way, just like the rest of the film. There is nothing in there that could make you laugh and nothing that 'thrills' you.
So my advice is, DON'T WATCH IT!