L IKE me, you probably laughed when you first heard a celebrity call themselves a sex addict. Shame's director Steve McQueen certainly says he did.

But then he started to look into the subject. And this spectacularly bleak, haunting film is the result.

Michael Fassbender is Brandon, an affluent New York office worker whose addiction to meaningless sex reduces him to a friendless shell.

Apart from awkwardly accompanying clumsily philandering married boss David (James Badge Dale) – the nearest he has to a friend – on trawls for women, Brandon spends his days scanning the internet for pornography and his nights searching for one-night stands with prostitutes and other strangers.

The sudden arrival of his needy sister Sissy (Carey Mulligan) and an attempt to date co-worker Marianne (Nicole Beharie) throw his ritualistic life into disarray. His sexual escapades spiral out of control as his lack of emotions begin to threaten the people around him.

McQueen's film, co-written with Abi Morgan, writer of The Iron Lady and the TV's The Hour, is beautifully directed and has lots to say about life in 2012: communications technology which ironically keeps people alienated from each other, the atomisation of relationships, the consumerist need for instant gratification.

But it is mainly about sex addiction, relying heavily on the acting – principally an awesomely focused turn from Fassbender. What motivates Brandon is never made explicit. But the weight of his clinical, heartless compulsions are written all over Fassbender's face. This is an actor who doesn't need words to tell you exactly how he feels and McQueen wisely lets him take the burden of a film in which he is frequently the most impressive element.

Mulligan convinces in yet another "long-suffering female sidekick" part, but one with such rigorous demands it shouldn't be overlooked as juries rush to load Fassbender with prizes. James Badge Dale and Nicole Beharie are flawless in support.

The sex is graphic and Fassbender and his co-stars often naked.

Quite honestly, however, this is one of the least sexy movies you'll ever see. Grief and misery underlie every second.

Brandon is trapped by his suffocating lifestyle and utterly isolated.

Coolly efficient at zeroing in on new sexual targets, he becomes monosyllabically awkward when attempting normal conversation and signs of emotional warmth trigger rage and despair (his awkward meal with Marianne is the most cringe-inducing movie date since De Niro took Cybill Shepherd to the pictures in Taxi Driver).

Occasionally, the spell breaks. Mulligan, a great actress but sub-average singer, seems out of her depth in what is clearly intended to be a pivotal scene. And McQueen, while completely non-judgemental of his characters in individual scenes, seems to impose a kind of Victorian moralism with the very arc of his slim story.

But, like Travis Bickle – or Julian in Taxi Driver writer Paul Schrader's American Gigolo – Brandon is a lonely figure who sees himself as apart from, or superior to, a society of which he is really the purest symbol. He's in Hell. And you'll never forget him.