The Watcher

If I were making a film of Janice Galloway's memoir, This is Not About Me, that is where I would begin. It would be a warm night on the first day of the Glasgow fair – not the way it used to be, with packed trains from Central Station decanting holidaying families all day and B&Bs with "No Vacancies" signs in the windows, but as near as Saltcoats ever gets to that these days. Across the water, Arran would be slipping into the darkness, the "mother funker" – as the waltzer proclaims itself – would be a whirl of coloured light bulbs, Dizzee Rascal blaring out of the speakers, and a few girls screaming, some trying not to be sick.

Fade and spin back 45 years. Still the waltzer by the sea wall, but this time the camera would be focusing on Cora, Janice Galloway's sister, then 22 and training to be a secretary. The camera would love Cora. She's over-the-top, glamorous, sassy, streetwise, rebellious, independent, free-spirited. She's gallus, spiteful, selfish, resentful, difficult, abusive. She stalks the pages of one of the sharpest childhood memoirs you'll ever read, walking out of it on steel-tipped stilettos straight into the imagination.

"Cora always attracted attention," says Galloway. "The one way she could rise above her fate was by glamour, by being jaw-droppingly, outrageously astonishing. Everyone in town must have known who she was. She was the only person I knew who went shopping in party frocks, dirndl skirts and a scarf. She was noticeably different."

She also attracted trouble. "You know that old-fashioned idea of women who were 'asking for it'? Cora was tailor-made for that. She wasn't 'asking for it', just exercising the only power she had – her sexual power, her ability to command a room. She could be funny and drink people under the table. That was her idea of being in control."

One thing about Cora and the waltzers. Whenever the leather-jacketed fairground hand gave the waltzer she was in an extra spin, she'd just laugh, cool as you like. No way was she going to give in and squeal like a little girl. No way was she going to be frightened when men followed her home in the shadows. No way.

Cora's dead now, yet in her sister's book she's larger than life: caustic, domineering, defiant. From its cover, she stares out autocratically, plucked eyebrows imperiously arched, dressed for a night out and impatient to go. Janice, a timid-looking five-year-old, shy and blushing at the camera, her feet barely reaching the floor, is squashed on the living-room sofa between Cora and their mother.

The first time I saw that picture, I overlooked the child in the middle of the sofa and thought Janice was Cora. It's an easy mistake. If you've ever heard Galloway read from her work, if you've ever read her novels (her last, Clara, is for me the finest Scottish novel of the last decade), you'd probably make it too. You'd be looking for someone who isn't going to smile conventionally for the camera, but is capable of staring it down. Someone who looks as though they're going to stride off confidently on a different path to the rest. Someone self-possessed, undaunted. Someone like Cora – or at least like her picture, her carefully tailored exterior. It's almost a shock to realise the guarded, expressionless child is Galloway, not yet having learned the tricks that would conceal her shyness.

Memoirs about childhood (and this one ends when Galloway is 11) tend towards the elegiac. Summers are endless and sunny, the world is a wide playground of innocence and wonder, paths into its blue remembered hills full of adventure. Not here. Instead, Galloway takes her readers straight back into childhood's wincingly recognisable uncertainties, dislocations and disruptions. She had more of them than most.

She was a late baby ("my mother thought I was the menopause"). Her father, feckless and heavy-drinking, had bought a small newsagents almost next door to the pub where he drank its profits. After 22 years, her mother left him, taking the four-year-old Janice with her. The only place they could find to live was a box room above the local doctor's surgery. It had a two-ring hob and a sink behind a curtain, a divan settee: no toilet, no bathroom.

She hadn't been a wanted child. If her mother had known she was pregnant, she always said, she'd have done something about it. But that didn't register, not completely, not yet. She loved her mother and now she was with her properly: not sharing her attention with the newsagents' customers, not having to worry about her father's boozy rages. She looked out of the window at the main street, content to watch the world go by, listening to her mother clean the doctor's surgery downstairs, helping her with the washing.

Then Cora came back.

She was 21 and had left her husband and a child behind her, hardly, if ever, mentioned ("Bloody weans! Who needs it?") and she crashes into the small box room flat, taking it over completely. Always quick with the smart back-answers and withering put-downs, always ignoring her mother's warnings, never any patience with anyone, let alone a sister too young to bother with. And that four-year-old girl, unable to understand the repressed emotions whirling round both that tiny flat and, when her father died, the house they'd lived in before, waited and watched. One day she'd make sense of it all.

WHEN we arrive in Saltcoats, she's under orders. She's to show me how it was in 1959, to tell me which supermarkets have to be reimagined into churches, which arcades had just opened for those strange new beings, teenagers, to point out the pub where her father drank, the houses she lived in, the box room flat, the Melbourne Caf, the shop she bought her first books in.

In 30 years, she'd hardly ever been back. In all of that time her childhood was dead to her, deliberately unexamined. Writing about it would, she tells me, have been as ridiculously revealing as playing poker and showing other players your hand, like saying: "Here it is – this is where the writing all came from." It might even, she sometimes thinks, circumvent the need for her to write anything else again. "The thought of stopping," she smiles, "quite appeals."

We drive past the estates on the hill leading down to the town, sunlight breaking through rain-heavy clouds to streak the sea silver ahead of us. Her aunts and uncles used to live here, near where the streets petered out into the countryside. There were shoals of children when Janice was growing up. In the older houses near the town centre where she lived, there were hardly any.

The Melbourne Caf , all chrome and hip in her memory, is now faded past its heyday, its paint losing the battle against the salt-coated wind. A couple of hundred yards away, the box room above the doctor's surgery is a nondescript office above a discount store with a remodelled faade. Over the wall of its back yard, the weeping angel of one of the graveyard memorials that used to give her a frisson of fear has now disappeared. So have most of the graves, their sheltering church now a museum, its graveyard a hoodies' hangout.

At Wellpark Road, the house they moved back to when her father died, two clumps of pink rhododendrons are outside the front door, two satellite dishes pointing out to sea from a two-flat terrace. And at this point I realise the essential futility of this journey. The book is so vividly written that reality can't compete.

I've concentrated on Cora because it's almost impossible not to. She's a force of nature, eclipsing everyone else. She must also have been hard to live with, and in later years Galloway became estranged from her. The reasons, she says, will become even more apparent in the second volume of her memoir, about her teenage years.

Yet standing outside the Wellpark Road house, I realise that I've misread the book. I've forgotten someone – the woman in the photo sitting at the other end of the settee from Cora.

If Cora was always going to attract attention, Mrs Galloway wasn't. She was a clippie, then a cleaner, then a school dinner lady. All her life she worked, and worked hard. It took its toll: the woman in the corner shop thought Janice must be her grandchild.

"She didn't want much out of life," says Galloway. "Just things she believed were hers by right – family, children and a lasting marriage. It didn't need to be wildly happy. It just had to last. That and enough material comfort to feel content. Not much – but even that seemed to slip her grasp." For all that, Galloway is at pains to point out that her mother had a formidable sense of the absurd: hardly a day went by without jokes, even if some were pointedly black.

Her relatives would have summed her up differently. Nerves, they would have said – because that's how people talked about depression back then when women suffered from it. "Of course, she suffers terrible from her nerves." That's what they would have whispered to each other when the ambulance called round to the Wellpark Road house and they were left to conjecture about the real reason behind the emergency.

"People tried to cover these things up, but they happened anyway. I had two aunties who killed themselves and male relatives who drank themselves to death – that's just the slow way." Had it not been for discovering the life-affirming power of music thanks to an inspirational teacher at Ardrossan Academy, she says, depression could have got the better of her, too.

Years later, that mousey, withdrawn girl has grown up to be a writer of unflinching honesty, graced by those habitual opposites, sensitivity and directness. You can see all of this in her new book. She may have changed the names of the people she's described, she may have had – of course she did – to invent some of those conversations – but the commitment to emotional truth, to describing what her childhood felt like, is there on every page.

It's there so indelibly because all through those years when those grown-ups nearest and dearest to her behaved in ways that didn't seem to make sense, she was endlessly watching, trying to taking everything in, to find out the rules behind the confusion. "I do remember," she says, "even then, thinking that watching was an act of resistance, that I was going to take all of this in and watch and make sense of it all one day."

You can trace that attentiveness in the face of the inexplicable in all her fiction, from Joy Stone in The Trick is to Keep Breathing to the unspeaking child who would grow up to become a virtuoso pianist in Clara. On a personal level, both motherhood and marriage to her opera singer husband, Jonathan, have left her happier than she's ever been. But watchfulness, that ability to look beyond the surface of things – if that has roots anywhere, it's in a child growing up with the mother and sister she had. And if, at the time, she didn't understand them, her portrait of them – thoughtful, empathetic, kinder than she might once have thought possible – shows just how much she does now.

The Germans have a word for that odd feeling you get when you go to a place you've read about in a book you love, when you find yourself there out of its time but in yours, accompanied by the ghosts of strangers you've read about but feel you know. Nachglanz, they call it. Afterglow.

On that July day in Saltcoats, as Janice Galloway posed for our photographer on the sands – bigger than she remembers it from childhood – that sweep round to Ardrossan, I got a hint of her book's afterglow. It was just the setting. Behind the sea wall, the waltzer – not the one Cora had been on, admittedly, but a successor – was nearly ready for another Glasgow Fair, lights about to be tested, sound system about to be switched on. In front of it, darkened apart from a shaft of light near the Arran coast, the sea. Forty-seven years ago, Galloway was just yards away from where she is now when her mother told her of her father's death. The sound of the waves on the shore wall almost drowned her words.

Two women. They're there on the cover of this book. One who asked too much from life, another who asked too little. In the middle, a young girl, growing up. Growing up to be a writer who would write the best, one of the most moving, yet completely unsentimental, accounts of growing up that you will ever read.

This is Not About Me by Janice Galloway is published next month by Jonathan Cape, priced 16.99. Janice Galloway is at the Edinburgh International Book Festival at 7pm tonight (sold out).