Claire Denis has confected one of the festival’s most unexpectedly delightful movies, showing in the Directors Fortnight sidebar. It’s an elegant, eccentric relationship comedy of ideas, highly rarefied and possessed of an almost inscrutable sophistication: the film has been co-written by Denis and novelist Christine Angot, reportedly inspired, in the loosest sense, by Roland Barthes’s prose meditation A Lovers Discourse: Fragments. The director has however warned audiences off the idea of seeing it as any sort of adaptation.

This is grownup film-making, more savoury than sweet, seductive, oblique and carried by a wonderfully smart and emotionally generous performance from Juliette Binoche – who delivers the material superbly, material which from almost anyone else would sound dyspeptic or absurd. (Isabelle Huppert would have been wrong in the role, though it’s amusing to imagine it.)

The drama (if that is the correct word) features Binoche as Isabelle, a divorced artist in Paris. She is now single, lives alone, and unable to decide if searching for the One is an urgent priority or a fatuity which is preventing her from enjoying life and experiencing pleasure. She has lovers and these liaisons are dangerous in that they don’t seem to provide the satisfaction they ought.

All the romance, the eroticism, the exquisite dissatisfaction of not knowing how or whether to be in love, is all dispersed into talking and debate and the intellectual interplay of ideas. Of course that may sound like an un-sexy ordeal and very French. And in blackest of black comic senses that is precisely what it is. There is more talking than sex, and that talk’s comic content is often dry as dust, mostly without the easy laughs and obvious comic beats of, say, Woody Allen or Noah Baumbach or Agnès Jaoui. But there are big, genuine laughs here, too: chiefly when Isabelle explodes with rage at an artists’ rustic retreat when one of her contemporaries gives vent to an insufferable discourse on his relationship to the countryside.

There is also an extraordinary, even experimental final credit-roll sequence when Isabelle visits a new age relationship therapist, played by Gérard Depardieu, a man with issues of his own who infuriatingly declines to commit to any specific advice, telling her to be emotionally “open” in a way that he might even be suggesting himself as a possible new partner. The credits on screen have an almost Brechtian distancing effect.

Isabelle has affairs with a conceited banker (Xavier Beauvois), a handsome but muddled actor (Nicolas Duvauchelle), a sensitive, gentle fellow artist (Alex Descas) and a sexy man (Paul Blain) who dances with her in a bar to Etta James’s At Last – to the peevish discontent of an unattractive gallery owner (Bruno Podalydès) who wants her for himself. These affairs are of course accompanied by conversations. But does talking fix what’s wrong in a relationship? Or is the neurotic need to talk merely a tragicomic symptom of its irreparable wrongness? Is the unexamined relationship worth having?

Isabelle’s encounters, sexual, semi-sexual and platonic are always accompanied by these agonised verbal bouts, in which putting the other person in the wrong is part of the contest. Isabelle goes to bed with her ex-husband and it all goes well until he tries to get her to have anal sex and she angrily refuses on the grounds that this is an exploitative new move he has “copied” – presumably from porn. She feels she is in the right. But he is aggrieved and she has hurt his feelings. And there is more argument, more talk. Painful for them, absorbing for us.

What a stylish treat this film is. It leaves you feeling sexier and smarter.