Call it kismet, but both Wanted and this week's Prince Caspian contain the same line: 'I was expecting someone taller...' The 'little person' in this case is James McAvoy, the Scottish actor who made his name playing Mr Tumnus in The Lion, The Witch and The Wardrobe.

What a difference a few years make. McAvoy, thanks to The Last King of Scotland and Atonement, is now hailed as the new Ewan McGregor. There may be jokes about his height in Timur Bekmambetov's fantasy action thriller but he's definitely the hero of Wanted.

Based on the graphic-novel series by Mark Millar and JG Jones, this film gets a lot of things right. For starters, it neatly recycles Fight Club's plot, offering up a disaffected, literate, hypochondriac dweeb, Chicago accountant Wesley (McAvoy), who is then transformed into a muscle man before our eyes.

Assaulted by flying bullets and dragged by Angelina Jolie into a fast car, Wesley is then introduced to a fraternity of killers who take their orders from a loom - yes, a weaving machine that sends encrypted binary messages via aberrant threads. Don't expect this to make sense but a lot is actually funny.

Wes has the blood of a killer flowing through his veins and must avenge his father's murder. His training, naturally, involves beatings. One of the fraternity ties him to a chair. "Is that OK?" says the tough-guy, brusquely. "Er, yes," replies the well-brought-up Wesley. He gropes for a suitable adjective. 'That's ... nice.'

McAvoy knows just how to deliver these lines - his wryness is thoroughly authentic. Jolie, meanwhile, is inhumanly beautiful, and even touching, as his brutal guardian angel, Fox. The actress seems determined to prove she's a babe with balls. Fast cars, huge guns, ugly tattoos, silly stilettos - she loves this macho horse-play and, because she happens to be talented, she can make some of it fun to watch. Fox and Wesley seem to come from different planets but spin round each other with grace.

Russian director Bekmambetov deserves praise, too. Wanted is shot with energy and style, the editing is flawless; the whole thing looks as crisp and tight as The Matrix. But most of the script is utter bilge water. If you've seen Minority Report, The Bourne series or just about any recent 'dark'; thriller, you'll spot the twist coming a mile off. Morgan Freeman barely surfaces from a coma of indifference and the jokes about Wesley's fat, female boss (which earned a round of applause at the screening I attended) are spiteful and witless.

So where does that leave us? Action heroes are often small (Tom Cruise is a little man and there have long been rumours that Sly Stallone stacks his shoes); Wanted, at least, acknowledges the missing inches - and does so with a smile. What a shame that, in so many other departments, it falls short.