Not bad at all. I liked the the way the writer gave subtle hints throughout the unfolding of the story. Little bits and pieces of the brother's sanity gone, each piece fading away with repeated alienation and the injection of his older sisters fantasy world putting the character at the brink of reality and madness. The concept of what he had done to the grandfather in itself is quite sick and demented, the story eluding to these acts as reactions to the actions of his narcissistic naivete family.
The story was quite awesome. Id like to see the writer paired with his thoughtful and creative equal for a director. Some shots were great while others lacked in or lessened the intended effect or emotion.
This is simply my opinion and if you don't like it then you don't like it and I could be totally
wrong about the writer's intention with his plot but again it is just my opinion (or what I took from the experience).
If you are even somewhat of a critical thinker and like a little mystery you may just enjoy this flick, and even if you don't like it at least appreciate the creativity of the writer.