Hang on to your seat back, your Bible, or the hand of a friend. Lars von Trier's Nymphomaniac bludgeons the body and tenderises the soul. It is perplexing, preposterous and utterly fascinating; a false bill of goods in that it's a film about sex that is deliberately unsexy and a long, garrulous story (two volumes, four hours) that largely talks to itself. Those naked figures in motion are just a distraction. To blunder in on Nymphomaniac is to catch the sight of a middle-aged Dane masturbating alone in a darkened room. It may be sensational, it might even be art. But I'm not sure it is intended for public consumption.

This, perhaps, is the corner that von Trier has painted himself into. Following his ejection from the 2011 Cannes film festival as a result of an ill-advised Nazi "joke", the puckish director has taken a public vow of silence. He has turned his back on the circus and pulled up the drawbridge. Nymphomaniac, for better or worse, feels as though it was made in a vacuum; a private shadow play, typified by theatrical dialogue and unvarnished editorialising. If von Trier can't speak to the press he can speak through his film. No interruptions, no questions. He is all set to splurge.

Charlotte Gainsbourg stars as Joe, a brittle, lonely sex addict (though she dislikes the term) who recounts her life story to Seligman (Stellan Skarsgård), her virginal father confessor. The film rewinds to Joe's youth, where she is played by British newcomer Stacy Martin (walking a teasing line between the enigmatic and the vacant) and prowls a non-specific city that looks European (the film was shot in Cologne) but adopts the pound sterling.

The drama is dark and heavy, marbled with contrivances and coincidences that the players remark upon and encrusted with a mixed-bag of supporting performances, from Shia LaBeouf (ill at ease) and Uma Thurman (electrifying) to Jamie Bell, curiously riveting as a neat little sadist who never once meets your eye.

Charlotte Gainsbourg with Jamie Bell in Nymphomaniac

Inside the monastic cell, our heroine spins the story of Joe in all its delirium and anguish. Seligman, meanwhile, hunches over her bed, providing an extended running commentary. He compares her odyssey to that of the whore of Babylon, the wife of Claudius, the compositions of Bach and the sport of angling. At one stage Joe recalls a contest with a friend, in which they scuttle through the carriages of a commuter train, seeing how many men they can screw. "That's a very clear parallel to fishing in a stream," exclaims Seligman. Joe shrugs and nods. She has no reason to doubt it.

How was it for you? How was it for me? Nymphomaniac doesn't care. It goes about things its own way, in the service of its own pleasure, manhandling the audience from one position to the next, occasionally snickering at its own private jokes and daring us to decipher them. Personally I found this a bruising, gruelling experience and yet the film has stayed with me. It is so laden with highly charged set pieces, so dappled with haunting ideas and bold flights of fancy that it finally achieves a kind of slow-burn transcendence. Nymphomaniac annoys me, repels me, and I think I might love it. It's an abusive relationship; I need to see it again.

Nymphomaniac is released in Denmark on Christmas Day and in the UK on 7 March 2014



• Xan Brooks reports from the first screening in Copenhagen

• Watch a video review of the film

• This article was amended on Wednesday 8 January 2014. We originally included a picture of actor Shia LaBeouf with a caption saying it was a still from Nymphomaniac. In fact the still was of LaBeouf's appearance in a music video for the band Sigur Rós. The picture has been removed.