Hamlet?

I don't really understand Hamlet. Throughout the play his character changes and from the moment he pretends to go mad I never know what his motives are or what he's really trying to accomplish. This isn't the first time I've read this play, and the last time through it I decided he was really crazy by the end. Where does he stop pretending? Between playing with peoples lives and getting revenge for his fathers death I feel like he gets lost in his own plan. I'm going to watch the Kenneth Branagh version tonight and I'm interested to see how he portrays the complexity that is Hamlet. We'll see what happens.....