One of my favorite lines from the ever-quotable Casablanca goes like this: the sniveling Ugarte, played by Peter Lorre, is trying to wheedle a favor from Humphrey Bogart's Rick, and he opens by counter-intuitively asking, "You despise me, don't you?" To which Rick replies, without looking up, "If I gave you any thought, I probably would."

That same dynamic is at play in the Vuillard family at the center of Arnaud Desplechin's marvelous new film A Christmas Tale, which has all of the ingredients to play like a typically uplifting fable about a dysfunctional family that comes together over the holidays to realise that love beats everything else, but none of the commercial cynicism. The Vuillards are much too screwed-up for a simple bit of third-act soul-searching to heal the wounds that have riven parent from child and brother from sister more or less since birth. This doesn't necessarily make it a more "realistic" work than the customary Hollywood pablum - Desplechin is too inclined towards exuberant absurdity - but it certainly feels more emotionally honest. Indeed, the extra pessimism and vitriol on display in A Christmas Tale somehow end up making it feel more genuinely uplifting than its American cousins - it's hard to relate to people who solve all of their problems in a tidy two-hour span, but people who have to work really hard to patch things up just a little bit are more more recognisably human, and it makes it much easier to believe that, yes, if they can, we can.

Explaining all the gnarled branches of the Vuillard family tree would be to rewrite the screenplay, but in essence: Junon (Catherine Deneuve) and Abel (Jean-Paul Roussillon) had four children, the eldest of whom died at six of leukemia. Their remaining offspring include Elizabeth (Anne Consigny), middle child Henri (Mathieu Amalric, who can also be currently seen as the villain in Quantum of Solace), and baby Ivan (Melvil Poupaud). Five years ago, Elizabeth bailed Henri out of some financial troubles with the stipulation that he would agree to being banished from her sight for the rest of time, and he's complied, even though he - like everyone else - has no idea what he did to engender such robust hatred from his sister. Meanwhile, her teenage son Paul (Emile Berling) is starting to suffer from apparent schizophrenia, just like Uncle Ivan, and there's some concern that he might be trying to kill himself: for some reason, this leads him to spontaneously make contact with the alcoholic, unstable Henri, just about the worst role model a young disturbed adolescent could hope to find.

The fun part, though, is that Junon learns just a couple of weeks before Christmas that she's dying of a particularly wicked cancer, and her only hope is a bone marrow transfusion that is almost as likely to kill her as the disease. It turns out that the only members of her family with compatible marrow are Henri and Paul, the least-fortunate pair of potential donors that could have cropped up (indeed, Junon's first response to finding that she has only those options to save her life is to announce that she'd rather die of cancer).

In the grand tradition of French art cinema, there's not a single one of these people who comes across as entirely good and noble (Abel is easily the closest), and the three figures that receive the most focus - Junon, Elizabeth, and Henri - are by a fair margin the most fucked-up of them all. Junon makes no attempt to hide her general disdain for all of her kids, particularly Henri (who, we're led to believe, was conceived solely in the hopes of providing a suitable donor for his doomed elder brother), and the siblings are locked in a race to see who can justify the other's neurotic hatred the fastest.

But at the same time, Desplechin is a born humanist, and while he's not looking to excuse his characters' deep flaws, he's not out to crucify them, either. This is actually a common thread in his films: we see the characters and know them to be jerks and failures and harridans, but we like them anyway: the writer-director (reuniting here with his occasional writing partner Emmanuel Bourdieu) doesn't paint in such simplified "bad vs. good" strokes.

At any rate, A Christmas Tale gives us a fairly rounded picture of unpleasant people treating each other poorly that comes across as buoyant and frankly joyful at times. No matter how much the characters might claim that they hate each other so much that they don't even bother hating anymore, there's still an obvious core of tenderness that's keeping everyone together, particularly in the film's best moment, a scene between Junon and Henri that begins with "I never loved you", "Me neither", and proceeds to gently undercut that essential concept. After all, if they all have such antipathy for each other, why would Henri consider for even a moment giving his marrow to his dying mother? Surely not because Elizabeth is right when she says he'd like to laugh over Junon's grave.

The writing and performances are all so self-assured here - especially Deneuve and Amalric, unsurprisingly, with a strong third-place finish by Desplechin's regular collaborator Emmanuelle Davos as Henri's latest girlfriend, the only genuinely self-aware person in this whole madhouse - that it's easy to overlook the minor but undeniable flaws in the film's aesthetic. This isn't nearly as tight a film as Desplechin's last, the 2004 masterpiece Kings and Queen (which shares a startling number of actors, themes, and even names with the newer film), not necessarily for bad reasons. There are a seemingly infinite number of stylistic quirks on display: split-screens, shadow puppets, irises, ironic musical cues (best use of bagpipes I've seen in a film in ages), and a few instances of characters directly addressing the camera, but after a while it seems likely that the director is chasing ideas down a few too many rabbit holes. Brilliant ideas that don't go anywhere aren't any less brilliant for it, but they also aren't really much to brag about, and while on the whole the end of A Christmas Tale leaves the viewer fulfilled and energised and a tiny bit hopeful (though, it must be said, likely a bit confused), it's nagging to me at least how many bits and pieces of the film didn't seem to end up at any place in particular.

In all honesty, though, I think this might be the kind of criticism that I'd only think to bring up in the full knowledge of how perfect Desplechin's filmmaking style could be. On its own terms, A Christmas Tale is still marvelous formally and as a story, further proof that the director is one of the great unsung heroes of the modern cinema. It's simply not like anything else out there, and it sets a pretty high bar for the rest of the holiday movie season to clear.