Hollywood dreams turn queasy in David Cronenberg's brilliant nightmare

Tea and absolutely no empathy … Julianne Moore in Maps to the Stars

David Cronenberg's new film here at Cannes is a gripping and exquisitely horrible movie about contemporary Hollywood – positively vivisectional in its sadism and scorn. It is twisted, twisty, and very far from all the predictable outsider platitudes about celebrity culture. The status-anxiety, fame-vertigo, sexual satiety and that all-encompassing fear of failure which poisons every triumph are displayed here with an icy new connoisseurship, a kind of extremism which faces down the traditional objection that films like this are secretly infatuated with their subject. Every surface has a sickly sheen of anxiety; every face is a mask of pain suppressed to the last millimetre. It is a further refinement of this director's gifts for body horror and satire.

Maps to the Stars has been written for the screen by Bruce Wagner whose Hollywood novels have the same sociopathically uncompromising quality, a gift for Tinseltown nightmare which makes Bret Easton Ellis look like Nicholas Sparks. At other times, this reminded me of Kenneth Anger, of Steven Bochco's pulp classic Death By Hollywood – which muses on the award-statuette as murder weapon.

The film is populated by a macabre gallery of Hollywood addicts: high-functioning lost souls at various levels of the totem pole. Julianne Moore is Havana Segrand, an ageing movie star who is supremely messed up and washed up, desperately waiting to see if she will be cast in a remake of a 1950s picture which starred her late movie-star mom Clarice, later killed in a fire, and of whom, with the help of creepy therapist Stafford Weiss (John Cusack) Havana has recovered memories of being abused. We see clips of this original film, evidently a melodrama in the vein of Suddenly Last Summer starring Elizabeth Taylor, and her mother – who appears to poor Havana in scary dreams and hallucinations – is played by Sarah Gadon.

Stafford's own 13-year-old son Benjie (Evan Bird) is the star of a hugely lucrative franchise teen-movie series entitled Bad Babysitter. Cronenberg shows how success has turned Benjie into the brattish Caligula of cute, and Wagner puts some of his nastiest zingers into Benjie's mouth. He has just sullenly undergone a summer of rehab and his PR-fuelled visit to the hospital bedside of a gravely ill fan is a gruesome fiasco, triggering hallucinations like those of Havana, with whom Benjie happens to share an agent. The event is an object lesson, provided right upfront, of this film's utter rejection of empathy in all its forms.

A newcomer to Hollywood, just in off the bus, is Agatha, played with scary intensity by Mia Wasikowska, who on making her entrance, turns her face into the sunshine and reveals something sad and distressing about herself, something which explains her preoccupation with Hollywood perfection in general and Havana in particular, with whom she manages to wangle a personal assistant job – thanks to a personal connection with Carrie Fisher, the one star permitted to play herself. Playfully, Wagner and Cronenberg allow us at first to assume that this acquaintance is mere fantasy. Fisher's appearance on the screen also provides a resonance with her mommie-dearest drama Postcards from the Edge. Almost immediately upon arrival, Agatha chances across Jerome Fontana (Robert Pattinson), limo driver and resting actor, with whom she begins a tense friendship. (It is an amusing twist on Pattinson's role on David Cronenberg's previous film, an adaptation of Don DeLillo's novella Cosmopolis, in which he was very much the limo passenger.) Her relationship with Jerome is what is to unravel her employment with the mercurial Havana, and is at the nexus of a world where everyone seems to be part of the same cousinhood or siblinghood of fear – one big unhappy dysfunctional family.

Agatha is at the centre of the film for another reason: she is a personal assistant, or, in the cynical slang, a "chore whore", someone very different from the gallant courtiers that attend Gloria Swanson in Billy Wilder's Sunset Blvd. Their job is to run errands, pick up dry cleaning, to flatter, to soothe, to be humiliated and to absorb all manner of demeaning abuse. Poor Agatha is witness to Havana's lavatorial eccentricities. Chore whores dream (like everyone else) of having their screenplays produced and imagine that their abasement will be repaid someday. In this movie and Wagner's other writings, the personal assistant is the authentic grisly image of modern Hollywood. In a perverted way, she or sometimes he is the true spouse, the true intimate, sub to the star's dom, privy to their dreams. In a world of air-kisses, this is the most viscerally real relationship, and the most transgressive and queasily tragicomic.

Maps to the Stars is a tense and scary movie, unwholesome in the hold that it has on the audience. Perhaps, in the end, it is too extravagantly cynical to be entirely truthful about Hollywood and LA, but it has a Jacobean power, the kind of thing that John Webster or Thomas Middleton and William Rowley might write if they were living in the 21st century: a claustrophobic nightmare of despair.