The movie was very captivating. It made me very uneasy from the onset, which is a compliment. Each scene seemed to be constructed to divert the audience into thinking the obvious outcome, but then left me with doubt. The acting was excellent.
The only minor flaw, was that I felt that this concept, a person suffering from mental illness lived in a world of his own making, has been used before in movies. Such as the movie with John Cusack.
I think great movies make you talk about them days after, and this movie achieved this with me.