What cruel, but commercially valuable timing Tanya Ronder's adaptation of D B C Pierre's terrifying, black comedy novel enjoys! The award-winning Vernon God Little not only shows how Pierre's scape-goated, eponymous hero is driven to death row by gross miscarriages of justice, after his best friend, Jesus, has shot dead 16 of their teenage classmates in a Texas school.

It also comes to the stage just weeks after the comparable, real life murders on a university campus in Virginia, where another youngster ran fatally amok. Pierre's fiction and Ronder's adaptation, as the remorseless hustle of Rufus Norris's powerful production kept on reminding me, proves even more shocking than Virginia's awful reality.

I kept giving in to shudders of amusement and laughter at this gross but believable picture of the disunited states of America. It will touch important chords with the young. Here on stage, sometimes admittedly rendered in the cartoon style of a Sixties comic-book, is an America possessed by immorality and greed, where life is enthusiasticallypractised as a low-grade branch of showbusiness.

Those traditional pillars of society, the family and church, police, law courts and medical practitioners, are all found crumbling and rotten.

Vernon God Little, in common with the disappointing Absolute Beginners at the Lyric Hammersmith, depends on a first-person, teenage narrator, the oddball outsider, Vernon, fired with brilliant contempt for society and adults.

Pierre's novel adapts far better to the stage. However much Vernon's savage tone of voice is missed, the inexorable rush of dramatics holds you in its disturbing grasp. Designer Ian MacNeil goes in for a bleak, bare stageing, with just a couch that revolves to become a car, a doorframe or two and a little back projection for the idyll in an unspoiled Mexico to which Vernon briefly escapes.

Colin Morgan, who has not even graduated from drama school and takes the title role in a stage debut of dazzling conviction, inhabits this limbo world. He is by turns phlegmatic and cynical, disparaging and disconsolate, even defiantly dancing at death's door.

Serene country music keeps being sung and played in ironic counterpoint to on-stage hysteria. Having left class on a teacher's errand before Jesus started shooting, and being delayed from returning by diarrhoea, Vernon finds himself accused of being an accomplice.

In an echo of McCarthyite America the accusers are unerringly believed. Questioned by the sinister female, Vane, done over by the thuggish Sherrif, sexually abused by the shrink to whom he is entrusted by the judge, Vernon finds himself stranded in the nightmare grip of American authority. Having been branded a murderer, they then cook the evidence to support the unjust verdict.

Everyone has it in for him. At home, a scene of cartoon-like grossness, Vernon's husbandless mother, Joanna Scanlan's plump, self-pitying Mom, welcomes her new fridge, her lurid neighbours and Mark Lockyer's fraudulent gentleman caller: this TV performer lies to the manner born.

Unfortunately Ronder's adaptation draws away from the original and close to the grotesque, particularly in its closing sequences. After Vernon has been betrayed by Mariah Gale's seductive femme fatale, he is absurdly subjected to electric shocks in court.

Death Row becomes Celebrity Big Brother, with millions of viewers deciding who should be the first to cast out of life. The finale comes, though, like joyful dreamlike relief from the grip of Pierre's dark, enthralling satire.