His Dark Materials, NT Olivier, London<br></br>Star Struck/ The Wicker Woman, Jermyn Street, London

It's been an arduous journey, but Lyra and Will wouldn't settle for anything less. His Dark Materials, Philip Pullman's trilogy of metaphysical adventure novels, has finally made its stage debut. Technical hitches delayed the opening last month, but Nicholas Hytner's "unstageable" double bill is now very much open for business. Everything seems to be running smoothly, although the set changes, while out of sight, are generally not out of ear-shot: there are thuds and rumbles long before Lord Asriel raises his army against the Authority. Still, it's a quibble, and quibbles are really the only kind of complaint you can make against Hytner's bold and solidly enjoyable epic.

A coming-of-age story with a difference, Pullman's irreligious universe of parallel worlds and humans that are ultimately stronger than their creator, has enraged a few and enchanted many. The main protagonists are Lyra and Will, two 12-year-olds living in similar but separate worlds, whose lives cross when their individual odysseys - Lyra's to join her uncle in his quest to discover the secret of Dust, Will's to find his long-lost explorer father - start following the same calamity-strewn path. It's a path that leads to a new world order, but they follow it in all innocence of their pre-ordained destinies.

Nicholas Wright took on a mighty task adapting this dark material. Did he stay true to its spirit? Well, yes and no. With three hefty volumes condensed into two three-hour plays, naturally much is excised (whole story strands and characters have got the chop). And Pullmanites may be outraged that Lyra and Will have been rewritten as twentysomethings. But once you've adjusted to another person's interpretation, it's clear that Wright's done a pretty faithful job, and Lyra and Will's grown-up reminiscences - which neatly frame the action - only add to Pullman's poignant ending.

There's more humour in the stage version. Sometimes this is to the play's advantage: the two angels, Balthamos and Baruch, are camp as Christmas and Lyra has a wonderfully sarcastic line about Lord Asriel's somewhat wanting pastoral care: "I saved his life. You'd think a postcard wouldn't be too much bother." At other times the humour backfires: the church dignitaries are cartoon baddies, a bunch of comically sinister prelates, their daemons (in Lyra's world, a person's soul takes the form of an animal) a selection of ugly, slimy reptiles. Hytner clearly wants us to mock their reactionary ways - and other things besides: the President of the Consistorial Court (Stephen Greif) is American and quite the hawk - but his jesting makes Pullman's secular vision seem horribly reductive.

Inevitably, some of the magic is lost in the extra exposition needed to keep the story moving, but Hytner never slackens the pace and his main actors, crucially, are captivating. Anna Maxwell Martin proves as bolshy, impetuous and heartfelt a Lyra as anyone could hope for. Her partner in crime, Dominic Cooper's Will, is similarly persuasive. Their scenes of burgeoning affection for one another are unsentimental and touching. Patricia Hodge perfectly captures Mrs Coulter's malevolent love (but doesn't quite convey her hypnotic charisma), while Timothy Dalton's gruff, no-nonsense Lord Asriel is a rugged breath of fresh air as he sweeps arrogantly into the midst of the stuffy scholars. He's less convincing tackling some overblown "Once more unto the breach"-style speeches, but the fevered urgency with which he pursues his quest to build "the republic of heaven" is infectious.

Iorek Byrnison, the ostracised armoured bear, is at first disappointingly human-sized, but Danny Sapani invests his role with so much grisly gravitas, you soon forget he's of normal stature. The witches have no grace, coming on like the sexed-up cave-women of that Lynx deodorant ad. Stephen Greif's Lord of the Gyptians lacks the dignity Pullman afforded the character and Chris Larkin's Jopari is a sham of a shaman, exuding all the depth and wisdom of a Hogwarts' trainee wizard. Still, John Carlisle has Lord Boreal's unctuous ways down to a tee and the hideous Cliff-Ghasts and Harpies should put the frighteners up a few young 'uns.

And the daemons? They are delicate wisps of puppets, their faces lit from within and animated by actor-puppeteers or manipulated by their human other halves. Some work better than others and the lightning-quick transformations that the children's daemons are capable of would undoubtedly be better served by film. But they are nevertheless a palpable presence.

Giles Cadle's designs, making full use of the Olivier's dramatic drum-revolve, are literal but satisfying - sturdy mahogany for the study in Jordan College, a grimy bus stop for the Oxford that exists in Will's world, and a sky magically split in two as the Subtle Knife slices through into another realm. Citagazze, the world plagued by soul-sucking Spectres, feels insubstantial and the grotesquely gilded palace of the king armoured bear is curiously understated. The most arresting image is that of the boatman in the Land of the Dead, rowing towards the children in a smoky beam of light, the sombre mood accentuated by composer Jonathan Dove's mournful trombone solo.

In the same scene, Lyra asks her Death, a physical being, to appear before her, a moment ingeniously realised on stage with her daemon, Pantalaimon (Samuel Barnett), ripping off his mask to become yet another integral part of the girl. It's at moments like this, when a simpler, uniquely theatrical kind of magic is explored, that Hytner's production can elsewhere seem too slavish to the text.

On an enterprise so weighted with expectation, Hytner cannot hope to please everyone. But watching two impressionable young things go into battle against good and evil and cast off the yoke of adult superstition, hits a lot of right buttons.

David Benson is in confessional mode. He is obsessed with "dead, camp comedians" and he wants to tell us why. The performer has made his name imitating the likes of Frankie Howerd, Noël Coward and most famously, Kenneth Williams in Think No Evil Of Us. His one-man shows charmed, not simply because they uncannily conjured the dead, camp comedians in question, but because Benson imbued them with so much recognisable, warts-and-all humanity. With Star Struck, he's shaken things up a bit: Benson's brought in Peepolykus director David Sant, who has coaxed some warts-and-all self-analysis from the actor. Thus we learn that Benson's life-long infatuation with the stars of the screen was born of crippling low self-esteem as a child. These revelations are interesting enough, but Benson is awkward in improvisational mode and the jokes tend to fall flat. Things hot up once the party gets going - a soirée at Coward's house featuring the impersonator's wish-list of A-listers. Benson does a lovely job flicking between a not-all-there Judy Garland, a savagely charismatic Frank Sinatra, Coward in flustered host mode and an eager young wannabe called David. What Benson has to say about the perils of celebrity worship is hardly earth-shattering, but his party is a blast, and in our relentlessly star-struck culture such sentiments arguably bear repeating.

What doesn't bear repeating is a viewing of The Wicker Woman, also directed by Sant. I first caught the show in Edinburgh last year and laughed my head off. It's a gloriously silly spoof of that scariest of scary movies, The Wicker Man. The very likeable Lucy Montgomery, James Bachman and Barunka O'Shaughnessy play a whole gallery of absurd characters, all with a deadpan twinkle in their eyes. Perfect for a light-hearted night out, but it doesn't stand up to closer scrutiny.

'His Dark Materials': NT Olivier, London SE1 (020 7452 3000), in rep to 20 March; 'Star Struck'/ 'The Wicker Woman': Jermyn Street Theatre, London SW1 (020 7287 2875), to Saturday