The Reader, Stephen Daldry, 123 mins, 15

A boy's passion gives way to grown-up German angst as his former lover's ugly past is revealed

(Released by Entertainment Film Distributors)

After a glut of festive frivolity, the detox programme that is the Oscars run-up begins with Stephen Daldry's spare, sober The Reader. Based on the 1995 novel by Bernhard Schlink, The Reader features the uncomfortable pairing of sex and the Holocaust – but don't worry, this is not The Night Porter, although it is perhaps just a step away from being Last Tango in Nuremberg.

The story's hero is a 15-year-old German boy, Michael Berg (David Kross, a young actor with a puppyish touch of Michael York), who in 1958 embarks on an intense relationship with an older woman, Hanna Schmitz (Kate Winslet). They spend a torrid summer – sex after school, followed by sessions of him reading aloud to her from favourite books. It's only later, when Michael is a law student and Hanna is on trial, that he discovers the truth about her: she was an SS guard during the war.

Hanna's crimes and their context are the subject of the film's second half, yet you might well come out of The Reader thinking as much about the curve of Winslet's naked hip as about the horrors her character presided over. But that's the point of the film, and the novel: the disjunction between the sexual being that Michael falls for in the bedroom, and the person he learns about in the courtroom.

What Daldry's film doesn't do, as some have – Sophie's Choice most egregiously – is to exploit the Holocaust as a background for a story of vicarious emotional awakening. What happens to Michael is more a political and philosophical matter: a young German's realisation that he needs to look beyond his cushioned post-war world, and to ask questions about history and the nature of law. The Reader hooks you with sex in order to get you thinking about ethics: only in Oscars season can a film get away with such a worthy agenda.

The trouble is, though, that this doesn't leave the film with a great deal to show us. The episode at the heart of Hanna's trial concerns her part in the death by fire of prisoners under her surveillance. Mercifully, and wisely, it's an episode that Daldry's film declines to show us. We hear about it, and see Hanna's reaction to its being discussed, but that's all.

Yet this means that the film's most memorable visual content is the rather glumly decorous sex of the first part. Kross's sweet-natured eagerness and Winslet's thorny detachment never quite bring their affair alive. And, while this is never a problem in the novel, on screen there's something a little precious about the reading sessions.

Oddly, Michael reads to Hanna from English-language editions of Huckleberry Finn and Tintin, and later, Hanna's prison library seems to be stocked entirely with English books. This incongruity signals the film's linguistic confusion. The Reader is cast with German actors speaking English, and English actors pretending to be German. Hanna's reality as a character is compromised by Winslet adopting a slight but distinct German accent. Meanwhile, Bruno Ganz, as Michael's law professor, may be a sublime actor in his own language, but in English he sounds like a strangulated troll.

The film seems unsure whether it's a transatlantic prestige movie, or the German art-house film it sometimes resembles: in the 1960s sequences especially, there's a definite hint of the spareness of The Lives of Others. But why not just make the film in German, rather than this awkward compromise? The answer, I suspect, is fear of alienating Schlink's substantial constituency among Oprah viewers.

I'm not convinced that Hanna is the tour de force that Kate Winslet might one day deliver. As Michael's inamorata, she's prickly and a little too mercurial to convince. But in the courtroom, her Hanna moves into a subtler register, at once confident and quietly uncomprehending; what makes these scenes so strong is that Winslet plays them matter-of-factly, as if Hanna were attending an unusually tense local council meeting.

Other plus points include Ralph Fiennes, playing Michael's careworn older self with a solemn detachment that marks him as an exemplar of what you might call the Reliable Family Solicitor school of acting – and I mean that as a compliment. And David Hare's script effectively distils the book's prolix and often overstated moral wrangling, especially in a tautly provocative last-act speech from Lena Olin as a Holocaust survivor: "My advice is – go to the theatre if you want catharsis." Daldry's restrained, serious-minded film deserves credit for refusing us such easy catharsis. But the result is honourable, studious, a little flat. The Academy voters will love it.

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