On page 20 of The Casual Vacancy, an adolescent boy has to clutch his bag close to his body on the morning journey to school "to conceal the embarrassment brought on by the heavy vibration of the bus".
Like the prisoners in Beethoven's opera, Fidelio - who emerge blinking into the sunlight to belt out their chorus of liberation - JK Rowling here hits the first note of her song of freedom. After more a decade within the gilded cage of the Harry Potter books and their richly imagined but strictly fenced world of magic and of childhood, how - in this first adult novel - will she use it?
The Casual Vacancy, which like that dawdling school bus in a smug West Country town, stops to pick up several characters and sub-plots on its route, nonetheless pivots on a simple story of rivalry over a parish council by-election. The contest proves in the end something that spurs the action along, rather than a page-turner in itself. It centres on whether the Fields - a disreputable, crime-ridden council estate on the edge of this postcard-pretty parish - should remain within Pagford or join the neighbouring city of Yarvil.
Before the vote, anonymous posts publicise the hidden shame of leading citizens, their "hypocrisy and lies", on the magic mirror of the parish website. Unaccountably, Rowling chooses to miss this opportunity to ratchet up suspense in a slow-moving plot, since we always know the how and why of every revelation.
This storm-in-a-teacup election will bring to a head all the festering tensions over class, family and status in a place of secrets.
Along the way, Rowling draws on her newfound liberty to touch on themes of heroin addiction, prostitution, drug dealing, Facebook bullying, online porn, self-harm with razor blades, child abuse and (almost in passing, but all the more shocking) the rape of a teenage girl. Motifs that recall Irvine Welsh in his transgressive pomp jostle with the Aga-saga social intrigues of Joanna Trollope - not to mention the Byzantine provincial politics of her Victorian ancestor, Anthony. Hogwarts Academy, initially, feels a million miles away. But, eventually, we will fall back into its emotional orbit.
Barry Fairbrother, beloved stalwart of Pagford parish council, has died of a sudden aneurysm in the golf club car park - a bolt from the blue worthy of Voldemort himself.
His surname welds the mislaid virtues of justice and fraternity: Rowling is not above a heavy dose of political symbolism. Barry has risen from the Fields to become both the local bank manager and rock-firm pillar of the community, free of the snobberies and resentments that toxify the town. So Rowling kills off her true hero at the start - a tricky, risky manoeuvre. His ghost, in various ways, will haunt every page.
In a swarming cast, some painted in perspective and others left as broad-brush cartoons, six clans dominate. Obese, bumptious Howard Mollison owns the upscale deli and new café - citadels of pretty bourgeois pretension - and treats lawyer son Mark as shoo-in for the "casual vacancy" created by Barry's death. Their respective wives, Shirley and Samantha (who runs an ailing outsize-bra shop), embody different generations of female discontent and disempowerment, with plenty of over-egged Mike Leigh-style comedy attached.
In the Old Vicarage live the Jawandas, the Sikh family of GP Parminder (and her scarcely visible heart surgeon husband). One of Barry's closest allies, Parminder finds that narrow-minded "Old Pagford" can never quite forgive her family for their "brownness, cleverness and affluence". But the solitary misery of daughter Sukhvinder means that the parent-child warfare that blights every family in this postcode won't stop at their Victorian door.
Up in their hilltop fortress, the Prices languish under the domestic tyranny of print-works manager Simon, a bullying crook. Young Andrew Price's smart, cool mate Stuart "Fats" Wall, son of the neurotic deputy-headmaster Colin and his guidance-teacher wife Tessa, rules the roost at Winterdown Comprehensive with his teenage existential cult of "authentic" behaviour - however cruel.
Stolid but shrewd Tessa comes close to this novel's moral core when she yearns to shout at clever, pitiless Fats, and the other kids, "you must accept the reality of other people... You must accept that you are not God".
Social worker Kay Bawden - presented for once with sympathetic insight - is an incomer from Hackney unhappily hitched to Mark's partner in the lawyers' office, the dithering Gavin. Her moody daughter Gaia, focus of classroom lust, longs for escape from this "fr***ing white" semi-rural backwater. And among Kay's clients are the Weedons from the Fields: chaotic, smack-using, on off prostitute Terri, her ragged little son Robbie, and Krystal, her disruptive, delinquent teenager. Krystal is, by a rubbish-strewn street, the most important living character here, both a diamond in the rough and Rowling's deliberate revenge on the "chav"-scorning fans of Vicky Pollard in that other "Little Britain".
Krystal, whom Barry befriended and encouraged to become a champion rower, again sports a symbolic name. Foul-mouthed but golden-hearted, decent despite all her deprivations, she represents the despised "underclass" that Pagford - that Britain - writes off at its peril.
Her very existence crystalises the character and morality of those around her. She separates the helpers from the wreckers, the sympathetic from the selfish; dare one say, the Wizards from the Muggles?
Rowling's writing, which can be long-winded and laborious in the clunkily satirical set-pieces, picks up passion, verve and even magic with Krystal and the other adolescents. Indeed, the teens of Winterdown belong in a bolder, richer book than some of the parental caricatures.
All the social and hormonal turbulence that the later Potter volumes had to veil in the euphemisms of fantasy appear in plain sight here. Slowed down by its fussy class geography and wheezing plot-motor, the novel builds into a vividly melodramatic climax with these kids at its heart. And after the convulsion comes a sentimental coda that, in tone and setting, whisks us right back to Hogwarts. Even if grudge matches at that school seldom gave rise to insults such as those on show here.