The female leads, the mother (Tilda Swinton) and the daughter, are given amazing, flawless performances. That mother is also given superb character development, and so is the son, whose unenchanted mood and the painful events he sees around his family fit very well with the ugly camerawork and shit weather. The captivating subject matter (the seldom-covered one of incest) keeps the movie edgy, even though the dialog and the pace are kept to a minimum. The direction style makes the whole thing feel realistic, and the focus on the boy made it feel like you really are in his shoes, while the complexity of his character (he was neither hero nor villain) made the movie all the more better.
I found it sad that the two female characters outside the family were thrown away without explanation, though they too were given good performances.