The progression of his thoughts and mind into brokenness was perfectly illustrated in what ends up to be a golden example of psychological horror, while still appealing to lovers of all horror genres (except the horrid campy ones). A must see of those who wish to be asking themselves "what is reality?" every time a thought of this movie comes up.
That doesn't rely on typical jump scares or gore, it's actually a mental horror. And great acting by cusack.