To nab Trevor Nunn for any production at your theatre is a real accomplishment. To get him to premiere a children's Christmas show is a tremendous coup for the Young Vic.

Skellig is based on David Almond's Whitbread award-winning novel of the same name, and from the start, you're reminded of another of Nunn's legendary literary triumphs: Nicholas Nickleby. That 1980 adaptation of Charles Dickens' classic has gone down in theatrical lore and, more recently, has been resuscitated for younger fans through a new DVD release.

Though Skellig never reaches the epic proportions of the eight-and-a-half hour Nickleby (even if, at two-and-a-half hours, it still feels like a mini-marathon, especially for its restless target audience), it arises from the same vein of 'story' theatre, and Nunn draws the comparison between the two productions himself in a programme note. Elsewhere, there are more visible similarities - the use of a multi-tasking, narrative chorus; an Aladdin's cave of a set (care of Nunn's old RSC associate John Napier) which brings the sights and sounds of the characters' world thrillingly alive all around you; and, last but not least, the presence of David Threlfall.

In Nickleby, Threlfall provided the story with its moral heart as the orphaned Smike. Here he plays the arthritic creature that young Michael finds in the dilapidated garage of his family's new house. It may be the title role, but it's a disappointingly small one for this fine actor, who's required to do little more than hide under a blanket throughout the first act. What's more, in terms of suspense, Skellig's mystery qualities come as little surprise after a barrage of ornithological references.

Title or not, this is Michael's story, and newcomer Kevin Wathen is a very good Michael, a sad boy who, confronted with the potential death of his baby sister, searches for courage and understanding. Akiya Henry as his best friend Mina exudes childlike glee and curiosity, if at times her exuberance could benefit from more containment, while Cathryn Bradshaw and Anthony Byrne as Michael's mum and dad touchingly convey a desperate parental struggle. They and the rest of the energetic ensemble also shift as necessary to become students, teachers, patients, doctors, construction workers, bus passengers and even owls.

It's an impressive array of talent and - bolstered by some enchantingly dramatic lighting, music and sound effects (Howard Harrison, Shaun Davey, Fergus O'Hare) - inspires a fair share of giggles and gasps of sheer delight. And yet, the real magic seems to have been lost somewhere between the page and the stage here. Perhaps Almond, who himself adapted the piece, is still finding his way with the new medium.

Yes, it's a refreshing and ambitious Christmas alternative but, while there are moments when Skellig flies (literally), it rarely soars as much as you want it to.

- Terri Paddock