This is the kind of movie critics can get excited about. All-around good performance by most actors, an ambiguous plot (either a murder mystery where a marshall is driven insane or really an insane man gets the chance to play out his fantasy) that easily lends itself to different theories of what is really going on. A brooding, gloomy atmosphere that manages to disturb most easy-going visitors.
Personally, I wasn’t so crazy on the movie. The second interpretation came in really late, but it was made pretty clear that this was the one preferred, invalidating most of the plot development and mental investment in the other story that went on before. The movie was too much buildup that essentially went nowhere. And the ending was such a cop-out. Instead of playing with the whole ambiguous angle, the movie made it pretty clear that yeah, he was insane before and he was healed and he wanted some peace so he initiated the lobotomy with his actions. Such a cookie-cutter Hollywood moment. A more appropriate ending would have been seeing him getting dragged to his operation, still screaming that he was a Marshall.