It's possible to read all sorts of things into Anna Paquin's extraordinary performance as Lisa Cohen, the lead character in Margaret: uncertainty, moral absolutism, the desire for love, the terror at showing any emotion that might mark her as vulnerable, enthusiasm for her own growth as a person, comfort in knowing that she is the pinnacle of human intellectual development. She is a 17-year-old, that is to say, and one of the very finest and truest teenagers that has ever been captured on celluloid: Paquin zeroes in on the exact mixture of arrogance and innocence and tenderness that can only be found in a late adolescent, and turns it into one of the most exquisite pieces of movie acting of two separate years.

Nobody can review Margaret without the tortured backstory of Margaret informing it; and on the one hand this is a fucking crime, because it turns one of the most original and heartbreaking and wonderfully messy & idiosyncratic films released in 2011 into the sum of its IMDb trivia section. But the story is important: following his dynamite 2000 directorial debut You Can Count on Me, Kenneth Lonergan contracted a bad case of the haughties; he filmed his sophomore effort in 2005 and 2006 in New York City, and proceeded to spend five years failing to bring it to a final cut that satisfied both himself and Fox Searchlight. After a process that we are likely to never fully understand, the movie has been given the kind of deliberately shitty release that a distributor holds in reserve for the kinds of troublesome films that they want to openly shame (one theater, one week per city). Which is where we are now.

If the exact version of Margaret that finally saw the light of day - which is not Lonergan's cut, though he endorses it - had come out on schedule in late '06, I think it would be easier to take it for being a marvelously ambitious and often terrifically flawed sophomore effort by one of our most exciting new directors. All those years of delays (for context: since Margaret entered production, Terrence Malick has released two different feature-length films) have turned into something more myth than film, and it's really not fair to Margaret, which is absolutely great, but does not in any way suggest that a half-decade of fussing went into its completion. More importantly, however good it is, it's not good enough to ruin a career over - and let's not be romantic about it, Kenneth Lonergan is probably not going to make another movie in America.

The film is about many, many things, but the nugget is that Lisa is a typically callow child of some amount of wealth who seems to have it in mind that she's just a regular girl trying to make it through the mucky world of post-9/11 NYC (among the film's most curious attributes: showing off just how much the cultural dialogue surrounding the War on Terror has changed since the dawn of Bush's second term). One day, she happens to spot a bus driver (Mark Ruffalo) wearing a hat she likes, and in trying to catch his attention, she distracts him during the exactly wrong split-second: he runs a red light, knocking over a pedestrian, Monica Patterson (Allison Janney), who dies in Lisa's arms.

This doesn't just turn into a crisis of conscience for the young woman: it creates a full-on existential nightmare in which she simply cannot deal with the fact that there are awful things that happen because the universe does not give a shit about whether Lisa Cohen or Monica Patterson is healthy and whole. This is the most reductive possible statement about Margaret, reductive to the point of being absolutely insulting; but there is so much going on in the film that it helps, I think, to have something firm to grip onto. Anyway, that is the key theme underlying all of the film's 149 implacable minutes: for all that it has to say about subjects as personal as the frustrations of being the child of an artist to subjects as universal as the confusion attendant upon developing into a sexual adult and as damn complicated as the moral way to understand the Israeli-Palestinian conflict, each and every single conflict can be drawn down to a single precept: Lisa wants things to be easy, and they are not. It is for this reason, in part, that the film is such a fucking fantastic depiction of teenage psychology: 17 is just about the last age you can get away with genuinely thinking things are so straightforward as Lisa does, and at any age, the discovery that they are not is an agony.

But even that is trimming it down more than it deserves: the only way to truly get how wonderfully complex Margaret is, is to watch it, and Fox Searchlight would prefer that you not do that.

The best thing about the film, indeed, is that it is so full of ideas, so very resistant to being pared down to basic principals: it is as novelistic as any film of recent vintage I have seen (but not bookish - Lonergan's delight in playing with cinema is palpable), crammed with a menagerie of amazing characters and peppered with episodic incidents that serve rather to give the film richness than to reduce it to a string of plot points. Matters as essential to the film as the conflict between Lisa and her emotionally absent actor mother, Joan (J. Cameron-Smith, giving a devastatingly good performance that deserves to make her much more famous than it shall do) rest comfortably alongside scenes that serve mainly to give it flavor - but what flavor! I particularly loved a scene in which Matthew Broderick, as an English teacher, shares with the class the famous lines from King Lear, "As flies to wanton boys are we to the gods / They kill us for their sport", only to content with a stubborn boy who tries to insist on a completely daft interpretation, anything to deny the simple message that life is that arbitrary. Yes, the metaphors in the film are all roughly that obvious - but Lonergan believes in them so much that we can't help but do the same. Two figures representing entirely different ways of understanding the world, Monica's best friend Emily (Jeannie Berlin) and Joan's new lover Ramon (Jean Reno), are both given the chance to seem completely reasonable and yet entirely wrong about their most basic assumptions.

And like so many of the sprawling 19th Century novels it evokes, parts of Margaret are tremendously bad: from something as petty as the fact that arch-Frenchman Reno is stunningly miscast as a Colombian, to something as confusing as the way that Lisa and Emily's friendship continues on after the scene where it very clearly blows up, to something as potentially destructive as the film's affection for scenes of people screaming curse words at the top of their lungs. Lonergan name-drops operas too much for us to miss the point: this is a torrid, heightened depiction of human emotions, and sometimes that is a bad fit for the low-budget pseudo-realism of the film's aesthetic. But sometimes it's brilliant. Sometimes the film's tendency to jolt from scene to scene, leaving key events hidden behind a cut, is chaotic and strange. Sometimes it transforms the movie into poetry.

It's not perfect; it's probably not even the best possible version of Margaret. It is, however, a singular triumph of filmmaking brio, the kind of film where even the flaws are so impressive that you would shrink in fear from changing something as tiny as the inflection of a single line. Perfect or not, it is essential cinema, and one of the singular achievements of 2006, 2011, and all the years in between.