Paper Cup by Karen Campbell review

A homeless woman makes a pilgrimage to return a lost engagement ring in this poignant novel

From Rachel Joyce to Jonas Jonasson to Emma Hooper, novels about older people going on long journeys have almost become a genre: later-life pilgrimage fiction. In Paper Cup, Karen Campbell gives it a new slant; her protagonist who takes an extended walk is a homeless alcoholic. The freezing doorways, dirty skips and uncaring streets of Glasgow are where Kelly sleeps and lives, trying and often failing to stay off the drink. Late one night on a bench in George Square, a drunk bride-to-be celebrating her hen night with a potty on her head and pockets full of cash accidentally leaves her diamond engagement ring behind; Kelly sticks it on her own finger and cannot get it off. A day or so later she flees the city, determined to return the ring to the bride before the wedding in a week's time. She travels south via a series of pilgrimage sites, and with the help of various characters, to Gatehouse of Fleet in Galloway, the town where she grew up and where her estranged family may still live.

Paper Cup is Campbell's eighth novel. A former police officer brought up in Glasgow, now living in Galloway, Campbell's love for Scotland – the people and the place – shines through.

It's Kelly's interior voice and her "notes to self" that lift this book, creating a character who is both vulnerable and striving to do better, so that even when she gets drunk enough to behave abominably, her actions are ultimately forgivable. Kelly uses the voice in her head to urge herself on, to shut down painful memories and to berate herself. "Kelly, Kelly. When did your life conspire against you? When did you start to pretend that drinking hair lacquer mixed with milk was fine?" But amid the vomit and the piss, her moments of pleasure are vivid and visceral, and the reader feels them even more for everything else that is denied her. The narrative focuses on the citrus creaminess of a plate of bread and butter pudding with marmalade, the architecture she notices as she passes through towns and villages: "The clock tower is square but flat on top, with weird rounded crenellations that splay like plumes. It stands alone, unsupported by any other building."

For all this, Paper Cup remains only just on the safe side of whimsy. Occasionally it strays into the realm of the inspirational quote. "If we all put something in the kindness bank, it's an investment, isn't it? Maybe it will be there when we need it," says one of the characters Kelly meets. Some of these people are unconvincing, too straightforwardly good or bad: the hippies who give Kelly a lift in their camper van; the posh Englishman whose dog Kelly steals; kindly Clara who makes her breakfast. And there are a few handy gaps and conveniences: Kelly rubs her finger with seaweed to try to remove the stubborn engagement ring, but never tries with soap in the various public toilets she visits. The biggest convenience of all is that the wedding just happens to be in the same town where Kelly grew up.

Despite these coincidences, Paper Cup is often a poignant and harrowing read. Campbell gambles on our empathy when she shows Kelly at her worst, and she wins because she has written, without judgment or criticism, an original and memorable protagonist; one who moves through a landscape described with love and care, and whose interior voice will continue to ring in the reader's head even after the long journey's end is reached.

Claire Fuller's Unsettled Ground (Fig Tree) won the 2021 Costa novel award. Paper Cup by Karen Campbell is published by Canongate (£14.99). To support the Guardian and the Observer buy a copy at guardianbookshop.com. Delivery charges may apply.