I too came to it via Geoff Thompson's book "Watch my Back". I abhor violence, but - so unexpectedly - I couldn't put the book down: I never expected a book on violence to be so spiritual as well as explicit in context. So I just HAD to see the movie - and I found it a compelling and moving watch, with added twists to make it great even though I'd read the book.
So my recommendation? Go for the hat trick: Get the book, the DVD and the music soundtrack all together here on amazon. You won't regret you did; in fact, I bet that you'll be back buying more for presents!