Personal Shopper was booed at the 2016 Cannes Film Festival en route to winning the award for Best Director for Olivier Assayas, both of which are exactly right. I would be inclined to call it not merely a great film, but a very great film, and comfortably the best thing Assayas has directed since 2002's demonlover. But it is not a movie that has any desire to be liked, or even particularly admired. It's a movie that's easier to define by what it's not, than by what it is: it's not a thriller, not a mystery, not an erotic character study, not an anti-capitalist satire. And the reason why it matters that we neatly sketch out that Personal Shopper isn't any of these things, is because the film does rather strongly imply that it's all of them, at one time or another.

As for what it is, let's go ahead and start at the level of plot, for want of a better place: Maureen Cartwright (Kristen Stewart) is a 27-year-old American living, for right now, in France. We can guess from the title that she's the personal shopper to some celebrity or another, and indeed this will prove to be the case: she zips all around Paris collecting the finest, most glamorous things for Kyra (Nora von WaldstΓ€tten), a famous model. But in the very first of the film's many violations of our expectations, we don't learn any of that for quite some while. Instead, we first meet Maureen in her second job as a psychic meeting, when she's sitting quietly in a haunted house, attempting to make contact with whoever remains behind. Oh, that's another thing Personal Shopper isn't: a horror picture.

Everything we learn about Maureen comes in through the side, as it were: explanations come after we've already intuited what we're looking at, or never come at all, and the plot of the film is a jumble of actions that we have to sort through later. There are a couple of reasons for this: one, not to be too cynical about it, is that Personal Shopper is a European art film, and Assayas is one of the current reigning European art film brand names, and The Done Thing in art cinema right now is to ladle up the ambiguity and avoid, like death itself, having to present a clear, linear plot. But there's actually a good reason, too, which is that Personal Shopper is intensely focused on Maureen - the film and the character are basically inseparable from each other, and one thing we rather quickly learn about Maureen, even before we pick up all the details, is that she's in a pretty bad way.

As it turns out the ghost she's trying to contact is that of her dead twin brother, who had a rare heart condition that she shares. Early on in the movie, she meets with a doctor, who promises that she'll live a satisfying, long life as long as she avoids exertion or strong emotions. This being a movie, even a French art movie, it is of course the case that she'll end up feeling strong emotions somewhere down the line, and while this conversation is never explicitly referenced again, it haunts (as it were) the rest of the movie.

So the thing that Personal Shopper actually is, as it turns out, is a paired study of stunned grief, and a morbid fascination with death and what comes after. It would trivialise Assayas's screenplay and even more so Stewart's outstanding performance - the best of her career, even eclipsing her last wonderful turn with the director, in Clouds of Sils Maria - to simply posit that Maureen wants to die, because she is sad, and also that she is scared to die, so she obsesses over the afterlife. But I do think that approaching the film with those ideas in your back pocket is the right way to get at what the film is gunning for.

The script of Personal Shopper is an amazing polyglot, including elements from several genres and shuffling through minor and major plot strands indifferently, while presenting a kind of overall thriller structure - Maureen is receiving increasingly intense, threatening text messages, and there is a brutal death somewhere along the way - which it resolves so flatly (and off-camera) that it rather seems like the movie is actively contemptuous of itself for including those bits at all. It's not even a bad thriller, at that: there's a scene involving a progression of time-stamped text messages that is just the most punishing thing.

Meanwhile, in a completely different movie, Maureen spends her nights in Kyra's apartment while the model is out of tone, eroticising the act of trying on fancy clothes and play-acting at having a different identity. One could rightfully complain that the film is comprised of scenes and plotlines that only intersect because they're all happening to Maureen, not because they obviously take place in the same narrative universe; but that's the thing, isn't it, they're all happening to Maureen. Without giving away what happens in the final scene, it seems clear enough to me that Personal Shopper is basically all about opening sequence and a closing sequence - and devastating final line, perfectly delivered by Stewart in a self-mocking monotone - that both refer to the same basic thing: Maureen's need to find her brother in the afterlife (the film blithely, banally accepts the existence of the paranormal without any hand-wringing), to assure herself that everything is alright, whatever "everything" refers to. And then the whole rest of it - murder and gorgeous costumes and nude scenes and sarcastic assault on the society that encourages such things as personal shoppers - is simply an explication of the feelings that the character leaves on full display in those opening and closing scenes.

Which brings us back to Stewart, who is utterly perfect. Technically, I suppose this role is actually more straightforward than the one she played in Sils Maria; an affectless void of feeling (not so far from what she was up to in Twilight and its sequels, really), punctuated at turns by fear and sexual arousal, all serving to keep a sense of existential panic tightly clamped down. It's got a lot of moving parts, but the choices Stewart makes are more or less exactly the ones you'd expect she would, from the script. Granting that, it's still a remarkable piece of character creation, for Maureen is hardly a straightforward character: we only get to see her grief at oblique angles, refracted through the film's indifferent application of genre elements. The results are, I would say, very much worth it, though a contingent of Cannes critics obviously would disagree with me. And in fairness, what Personal Shopper ends up revealing is pretty basic: young people are ill-equipped to deal with the nearness of death, and sublimate it in all sorts of frantic ways. Not exactly the most astonishing theme a movie ever had, but the sophistication of its presentation, and that powerhouse of a central performance, are absolutely enough to make the film amply worthy of more than the weirdly indifferent reception it's had to this point.