Saw this on the weekend, still thinking about it now. One of the best screenplays in a long time. Excellent acting, especially Nic Cage doing his trademark multiple personality acting. At first I thought the ending was kind of a typical Hollywood ending. But the more I thought about it makes me think that this was intentional as Charlie couldn't adapt the ending as the book had no conclusion. Then Donald took over the screenplay, so this is showing what he would write to make the film more conventional. If this is the case then the ending is genius.