A lot of reviews describe this film as a "moral tale". I agree, but the morals presented are not traditional morals. So while it's certainly a very good movie from an artistic and technical standpoint, it's not a good movie in the sense of upholding good morals from a traditional and religious standpoint as the movie does not hide its very open disdain for traditional Christian morals.
Which isn't to say that this isn't a religious movie. It's probably the most religiously devoted movie I ever watched. It's just that the religious values it promotes aren't Christian and nor are they from any other traditional religion, but go more into the direction of religions that in the past were considered to be more esoteric and occult and therefore have not made attempts to make mainstream Hollywood movies that directly outline their religious views and beliefs. To my knowledge this is the first mainstream movie that does so openly and directly.
Which isn't to say that it's not a very mysterious movie, but since it's so open and direct, the only mechanism it leaves for protecting its secrets lies in hiding them in plain sight. So when it comes to a lot of reviewers who try to figure out what exactly this movie is about or what even the story is exactly and what its purpose is - just actually and attentively watch the movie and just listen to everything it says - the movie tells you all of its "secrets" surprisingly directly - as these would of course normally all be deeply esoteric and occult and they are.
And of course this movie would not have been possible without Heath Ledger and his great sacrifice - I say that not only because right from the beginning the plot of the movie of course revolves around his character being sacrificed for his friends, but also because he sort of sacrificed himself for the movie in real life - as all the stress and effort it took him to try and finish the movie and give it his best, of course took a toll on him and of course contributed to his overdose and tragic death in real life.