The ellipsis in the title of Once Upon a Time… in Hollywood says it all. It confides a doubt or hesitation, or introduces a rupture that we have to wishfully leap across. Yes, Quentin Tarantino’s glorious and warmly generous film is a fairy tale – or at least it ends like one, with a confected epilogue to a massacre that lasts for fifteen floridly vicious minutes; but it is a fairy tale about Hollywood, where fantasy is an industrial product and the boulevards are littered with broken dreams.

Tarantino’s title salutes Sergio Leone’s Once Upon a Time in the West and Once Upon a Time in America, which do without ellipses: his Italian mentor was free to reimagine Hollywood genres while remaining at a safe distance from the place and its commercial imperatives. The fairy tale in the former film is the delusion of a crippled railway tycoon who hopes to span the continent with his tracks but dies crawling towards a puddle in the desert; in the latter it is an opium dream that mercifully blurs the truth about gangsterism and graft. Although the phrase of Tarantino’s title calls to mind a soothing bedtime story, the time he invokes is 1969, a year of acid-flavoured cigarettes, tacky clothes and jerky, frenetic dances, remembered in Los Angeles not for Woodstock or the moonshot but for the rampages of Charles Manson and his gang.

The film’s characters are Hollywood’s castoffs. Leonardo DiCaprio plays Rick Dalton, a superannuated television cowboy, reprieved by the chance to make spaghetti westerns for Leone’s low-rent imitators. Brad Pitt plays Cliff Booth, Dalton’s loyal but battered stunt double, reduced to a domestic dogsbody. Living next door to Dalton is Sharon Tate (played by Margot Robbie), a bright new luminary, due to be slaughtered by Manson’s bewitched minions at the end. The supporting cast is littered with illustrious corpses. Burt Reynolds died before he could film his scene as the moribund owner of the movie ranch where Manson and his groupies squatted, so Bruce Dern takes his place; Luke Perry, also now dead, appears briefly as a lame, greying cattleman in a television pilot. Steve McQueen makes a spectral return to life in the form of Damian Lewis, and the cocky kick-boxer Bruce Lee is resurrected by Mike Moh, only to be launched through the air to dent a parked car by Booth.

By rights it should all be a gruesome mess, advancing towards that night in August 1969 when Tate and her friends were randomly and obscenely murdered. But Tarantino averts that seemingly inevitable denouement: this is his fondest, breeziest film so far. Despite its length of almost three hours, it is dynamised by the drives Pitt takes through the smog-blurred days and smouldering neon nights of Los Angeles, and aerated by a camera that cranes aloft to float above the Hollywood hills, vaults over a drive-in movie screen and bumps down to ground in a parking lot where an oil well is pumping wealth out of the arid earth. Though the images never stop moving, every frame is potentially a still, crammed with more alluring, historically accurate detail than the eye can take in. The ear is bombarded too, and not only by the jazzy riffs of Tarantino’s dialogue. Television sets and car radios are always on, and the climax moves propulsively from the Mamas and the Papas crooning ‘California Dreamin’’ to the Rolling Stones warning ‘Baby baby baby you’re outta time’.

The performances are glorious. Pitt ritualistically removes his shirt, but his stoical good humour and gentlemanly tact matter more than his musculature. DiCaprio shows off his histrionic skills rather than his physique. His Dalton emotes explosively, lapses into maudlin self-pity and loses face – as Booth disapprovingly notes – by crying in front of some Mexican parking attendants. He swaggers when he remembers his lost mystique, fumbles as he realises who he currently is and, during a lunch break, humbly attends to a life lesson administered by his sagacious co-star Julia Butters, who was eight at the time of filming. In a corresponding scene, Booth picks up a nubile hitchhiker, in whose eyes he is a grizzled old-timer; she lowers herself onto his lap as he drives, but he demands to see documentation to prove that she’s over eighteen.

Robbie smiles, grooves and jives through the action, exuding an almost angelic goodness. A scene in which Tate goes to the cinema to see herself in a dopey, dated Dean Martin comedy ought to be a self-referential indulgence for her character and for the movie-addicted Tarantino, but it opens out into an enchanting demonstration of the way films can enlarge and transfigure life. ‘I’m in the movie, I’m Sharon Tate,’ she announces at the box office. She can hardly believe it herself and she is delighted to save seventy-five cents when the manager lets her in for free.

She has become the princess in her own fairy tale. Dalton enjoys a similar wish fulfilment: he morosely recalls that he lost the role of the motorbike-riding prisoner of war in The Great Escape to Steve McQueen, but then the film cuts to a scene from the actual movie, into which, with the help of some slick CGI technology, he has been transplanted. At the beginning of Once Upon a Time… in Hollywood we see a clip from a gung-ho action movie in which Dalton wipes out a coven of Nazis – a throwback to Inglourious Basterds, where Tarantino has Hitler incinerated, bringing the war to an early conclusion. At the end, Dalton enacts a similar kind of armed vengeance for real and ensures that some of the characters live happily ever after.

Here, however, is the problem: those three dots in the title cover an interference with history. Manson and his ‘family’ of feral dropouts are incidentally inserted into a film that has no need of them and is unable to comprehend them. The murders the gang committed were motiveless, not prompted by personal animosity, and the gratuitous terror they wrought is trivialised by Tarantino: he makes up a plot about vengeance and road rage in which Booth is roused to psychotic fury by the slashing of a tyre on Dalton’s 1966 Cadillac Coupe DeVille by a member of the Manson gang.

The sunny, ebullient Tarantino has no talent for tragedy, perhaps even no belief in the finality of death: in Pulp Fiction he reshuffles chronology to resurrect John Travolta after Bruce Willis has very emphatically killed him. Rather than encouraging speculation about human propensities, the violence in Tarantino’s films satisfies a strictly aesthetic need. If there’s a prolific body count, he said of Kill Bill, ‘you know you’re watching a movie’. The characters of Once Upon a Time… in Hollywood spend their time watching movies, making them or acting them out: this is Tarantino’s seductive substitute for living and his fancied antidote to dying. At one point, when we’re asked to believe a publicist’s deceptive cover story about Dalton, Kurt Russell, delivering the film’s sardonic voice-over narration, snarls, ‘That’s a big fucking lie.’ Of course it is – but you might equally well call it a myth, admire its grandiose effrontery and be grateful to Tarantino for so valiantly defending fantasy against the pesky intrusion of truth.