By Zoe Heller
Fig Tree, £16.99

‘If in doubt," the rubric runs, "ask the rabbi." That's not the way of things in the faith-forgotten Litvinoff family, who habitually return barmitzvah invitations with "There is no God" scrawled over the engraving. In Zoe Heller's cruelly clever new novel, Joel and Audrey Litvinoff are the (eponymous and tongue-in-cheek) believers. Theirs is the third generation to have rejected Judaism since Joel's refugee grandma caused a shanda (scandal), flinging her headscarf into New York harbour as the Statue of Liberty loomed.

It is radicalism that the couple have believed in for 40 years - though, post 9/11, shanda territory has shifted. Joel, the longstanding celebrity left-winger and hotshot lawyer, no longer commands the same activist admiration.The papers dub him "rent-a-radical".

At 72, he is defending an Al Qaeda camp trainee in a high-profile trial when he suffers a stroke in court. Audrey, daughters Karla - obese and downtrodden - and Rosa, along with reprobate, adopted son, Lenny - whom Audrey clearly and deliberately favours over the girls - congregate at the bedside of the comatose Joel. So, disturbingly, does a large, dreadlocked, black woman who may, or may not, have rights.

At this point, readers of Heller's last, Booker-shortlisted novel, Notes on a Scandal, will expect scant consolation to emerge from this fictional crisis.

Heller's gift is for chronicling come-uppance, for tarnishing the glamour she so deftly depicts, and for exposing the psychological flaws in characters she conveys with as much scorn as affection. An incisive, tragi-comic puppeteer, Heller writes like a dream, deploying words that are fine but nonetheless contrive to sit colloquially on pages that must be turned.

At times, however, her prose reads like a stab in the back from protruding bedsprings. One way or another, the alternative, anti-establishment thinking of everyone who loves Joel is thrown disturbingly into doubt. As he lies diminished, Audrey masks her vulnerability with a vicious tongue previously tempered by Joel's bonhomie.

Behind the bravado, she wonders what the Litvinoff principles have really achieved and whether she (a won't-cook-won't-clean feminist) could at least have stooped to buy the breakfast bialys her husband loved.

Audrey controls her daughters by criticism, and her son by smother love, so you could be forgiven for seeing Audrey as an extreme example of the domineering Jewish matriarchy she deplores. At which point, enter the rabbi: of all three grieving children fumbling their troubled ways forward it is Rosa who most outrages Audrey.

For Rosa, a slim, blonde former chip off the old activist block, has rebelled in the increasingly familiar way of her generation: fresh from four disillusioning years in Cuba she slips into a synagogue and finds herself... at home. Quite the most touching chapters of this richly satisfying novel find Rosa celebrating shabbas in a suburban rabbi's house where she is mistaken for a goy; or exploring her complex feelings about the educated Orthodox woman who "makes herself over as a medieval ghetto-dweller" and asks the rabbi rather than improvise a moral code.

In the Jewish context, Heller remains an unsparing examiner of attitudes and foibles. But she softens slightly - or appears to - as if she, like Rosa, salutes the elusive "delicacy of mind" that believes without fully knowing it is right.

Madeleine Kingsley is a freelance writer