Barely ninety minutes into the colossal three-hour run time of Beau Is Afraid, we’re treated to the sight of a man, clad like a child in oversized silk pyjamas, having his head repeatedly shoved against a wall, at the hands of a woman drenched from head to toe in blue paint. It’s an absurd image, one hardly out of character for an obstinately absurd film – and also oddly fitting. Fitting because, at about this point in watching the latest release from A24-darling Ari Aster, you’ll just about be wishing it was your own head being shoved against a wall instead.

“primed to leave you almost as bored as you will be bewildered”

The man in question is, of course, the eponymous Beau (Joaquin Phoenix), a twitchy, middle-aged paranoiac afflicted by chronic depression, anxiety… and a fairly severe case of mummy issues. He lives alone in a crummy apartment slap bang in the middle of a sordid dystopian cityscape, his interaction with other people apparently limited to passive-aggressive notes from the neighbours slipped under his door and weekly meetings with a therapist (Stephen McKinley Henderson). We meet him the day before he’s due to take a dreaded flight back home to visit his mum, a plan quickly derailed by misplaced house keys, stolen luggage and a catastrophically timed car accident. As he ends up bed-ridden in the house of two disturbingly charitable strangers (an excellent Nathan Lane and Amy Ryan), so begins a nightmarish descent into madness, one in which the lines between delusion and reality are brazenly effaced for us, as much as for poor Beau himself… who seems to want nothing more than a reunion with his (perhaps not so) dearest mother.

The whole package ends up as something resembling The Odyssey, by way of Lynch’s Eraserhead and the anxiety cinema of Charlie Kaufman, with a healthy dose of Kafkaesque existentialism thrown in for good measure. And, as a habitual Aster defender, it pains me to say it – but it’s also pretty dreadful.

If unwaveringly ambitious and (very) occasionally diverting, Beau Is Afraid largely registers as a sluggish assemblage of vapid theatrics, heavy-handed Oedipal angst and barely concealed misanthropy, primed to leave you almost as bored as you will be bewildered. At its heart, it’s a play on the picaresque, a shaggy-dog story whose very point seems to lie, at least partly, in its pointlessness; but, if there’s any fun to be had in ineffectual yarn-spinning, it’s one this film swiftly forgets in favour of its own self-importance.

“a sluggish assemblage of vapid theatrics, heavy-handed Oedipal angst and barely concealed misanthropy”

Phoenix, so often an actor of unparalleled subtlety, is left adrift at the centre of the project, in a performance that’s about as nuanced as the film’s title, asking little more from him than 179 minutes of perplexity and pratfalls. His Beau is a black hole of charisma, condemned by Aster to flail around like a headless chicken through absurdist metaphorical manifestations of his own miseries. What does Beau want? What does he need? Don’t expect the film to care – it’s far more interested in watching its protagonist be repeatedly used and abused than it is in imbuing him with anything even close to approaching psychological complexity.

The film’s ready slump into monotonous repetition comes close to obscuring the few things about it that actually work. Along with Bobby Krlic’s unnerving score and an imperious turn from Patti LuPone, there’s a handful of sharp visual gags (the standout being the fleetingly visible packaging of Beau’s sad little ready-meal) which remind us that Aster remains a filmmaker with a keen formal eye that’s sometimes able to break through all the self-indulgence. Nowhere is this more evident than in a haunting semi-animated interlude towards the middle of the story, which I’d laud if it were a short film – instead, it’s immediately followed by a big, ol’ Freudian shrug of a final act that, however self-consciously so, (literally) capsizes in its own silliness.

The more Twitter-literate amongst you might remember that the film’s working title throughout much of its production was Disappointment Boulevard. As no less than a fifth party exited the cinema during my screening, it started to dawn on me that maybe the studio should have stuck with their gut on that one. I may have made it to the end of Beau Is Afraid partly for the sake of this review – but I also did so in the hope that Aster would whip out some genius final move that might make the whole affair come together. How wrong I was.

Beau Is Afraid is in cinemas now.