The Illuminations, Andrew O’Hagan’s fifth novel, centres around the life of Anne Quirk, a woman whose past is slipping away from her. We meet her in sheltered accommodation in Saltcoats, North Ayrshire, fussed over by the well-meaning but officious Maureen whose attentions occasionally tip over into interference.

Maureen is fascinated by her neighbour’s mysterious past, documented by a series of evocative photographs. One of them “showed a kitchen sink with old taps and a pair of breakfast bowls waiting to be washed and a milk bottle filled with soapy water. The sink and its contents shone like nothing on earth…”

It is both the beauty and the irony of Anne’s situation that as her mind is disintegrating, these photos become the only physical trigger to her fading memories. She was, Maureen soon discovers, a groundbreaking documentary photographer in her heyday, whose reputation has fallen by the wayside. She also has a secret in her past, the details of which emerge in glimpses throughout the novel.

The Illuminations of the title refer to Anne’s desire to travel back to Blackpool, a city with emotional resonance for her, but they could equally apply to the flashes of lucidity O’Hagan handles with such delicacy in the text. He is master of the small observation that elucidates something bigger and his prose is lyrical and often very funny: “It was a constant battle in Maureen’s head, the wonder of central heating versus the benefit of fresh air…”

O’Hagan, who was shortlisted for the Booker in 1999 for Our Fathers, inhabits his characters with ease and is one of those rare male authors who does women as well as men. Anne’s mental disintegration is beautifully and sensitively handled, and O’Hagan charts its course with a poet’s precision and a journalist’s eye. “Nobody ever tells you the natural world has all the answers and keeps count of all the days… One minute, you’re getting on with your tasks, the jobs and the life and all your goals and one thing and another, then, just like that, you notice the smell of burning leaves as you walk past the playing-fields.”

Anne’s internal conflict is counterpointed by a second, interlinked storyline, which follows her grandson, Luke, a captain with the Royal Western Fusiliers, who is on a tour of duty in Afghanistan and part of a convoy taking equipment to the electricity plant at Kajaki. In contrast to the contemplative passages detailing Anne’s enigmatic past, the passages in Afghanistan are a blaze of action and banter. O’Hagan has clearly done his research and the life of a modern-day soldier is vividly (sometimes a touch too vividly) portrayed. “Scullion breathed out and nipped his cock,” he writes breezily. “If you nip your cock in the wrong place you get piss on your boots.”

The dialogue is fast, furious and shot through with a liberal scattering of obscenities and death metal references. But it is when Luke returns home to Scotland to visit his beloved grandmother that the novel really gathers pace. The uneasy shift from frontline battle to humdrum domestic existence and drunken nights in the pub is subtly drawn. “The noise of the fruit machine seemed to infect his sense of things, a robust, well-lighted anxiety in the corner.”

As Luke is trying to forget his memories of what he saw in Afghanistan, his grandmother is seeking remembrance of things past. When the two of them are reunited, they set out on a trip to a Blackpool guesthouse where Anne once kept a room and the long-kept secrets from her past begin to float to the surface of her fractured mind.

The Illuminations is a book at once both tender and ambitious. In the writing of it, O’Hagan has cast a shimmering light on love and memory, life and loss and on the secrets we keep from those closest to us, sometimes even from ourselves.

The Illuminations is published by Faber, £17.99. Click here to buy it for £14.39