Super 8, 111 mins, 12A

Remember that scene in I'm Alan Partridge when Alan walks into a stranger's room and finds it plastered from floor to ceiling with pictures of his face? Steven Spielberg must have been just as alarmed when he walked on to the set of J J Abrams' new film, Super 8. It may be produced by Spielberg, but it's such an obsessive homage to what he was doing 30 years ago that Abrams might as well have called it "Close Encounters of the Extra-Terrestrial Jaws".

It's set in an Ohio steel town at the end of the 1970s, a time when youngsters with shaggy haircuts and braces on their teeth rode around on BMXs. Six such youngsters, all in their early teens, are spending their summer making a zombie movie together. They argue, they flirt, and we're just settling into an affable coming-of-age saga when Abrams gives us, and his characters, a brilliantly staged shock. One night, when they're on location at a railway station, they're interrupted by a prolonged, fiery train crash that will have audiences ducking for cover. As the kids pick themselves up, something extra-terrestrial emerges from the wreckage – and the budding film-makers have caught it all on camera.

Super 8 is not so much a pastiche of Spielberg's films as a note-perfect impersonation. The period details are faultless, right down to the soft-edged, almost grainy look of the cinematography, while the toy-cluttered, wood-panelled suburban houses could well be old E.T. sets found in Spielberg's attic and glued back together. This imitation, as uncanny as it is, tends to keep the viewer at one remove from what's happening on screen. It's one thing for a writer-director to make a nostalgic film about his childhood, but it's another to make a nostalgic film about the way someone else has represented childhood already. Still, it must be said that Super 8 is a better Spielberg film than quite a few of Spielberg's. It has his humour and warmth, his patented air of magic and awe, his miraculously unannoying child actors, and plenty of deft, properly scary sequences, most of which keep the monster hidden.

It's so entertaining, that only in the closing stretch do you notice that the young heroes haven't actually done very much. After the crash, they keep on shooting their zombie epic as if nothing had changed, and, despite all the rushing around, you see that their actions have no effect on the Air Force or the alien whatsoever. Spielberg would not have made a mistake like that.