In another age Christina Patterson’s Outside the Sky Is Blue would have been marketed as a misery memoir. It’s true that it’s the record of a life that has contained an uncommon amount of misery. But this book is a bracing, heart-lifting read, a narrative that consistently, courageously rises above the horrors it recounts. Patterson is a superb writer – part of the redemptive message of this memoir is that beautiful prose can make almost anything bearable – but she’s also clearly a pretty wonderful human being. On page after page, she’s hit with the kind of sucker punches that would floor most of us, and yet she comes back sparkling with humour, with love, with hope. Outside the Sky Is Blue is a lesson in generosity, in accommodation, but most of all it’s a lesson in resilience.

Patterson’s story begins with the birth of her sister Caroline in Thailand. Her mother is Swedish, her father British and he has what promises to be a splendid diplomatic career ahead of him. Caroline is followed by Tom, and then Christina. By the time Christina is born, though, there are already signs that Caroline is troubled. Christina realises early on that her “skinny, sensitive, beautiful sister” is mentally ill, although the true extent of Caroline’s schizophrenia only becomes apparent when she is a teenager. Their father gives up his dreams of roving the world and settles down – grudgingly, we feel – to a job in the Treasury. Patterson reconstructs her childhood with a beautiful, sun-drenched nostalgia, summoning up holidays with her family in Sweden and a happy if shy existence in Guildford, drawing always on the rich store of her mother’s diaries and files. “My mother wanted to mark every moment of her life. She took photos of almost every meeting with a relative or friend.”

The trips to Sweden are a particular highlight: a delight at the time but also a rich store of happiness that the older Patterson is able to draw on in later, more challenging years. It’s not only that the holidays are glorious, it’s also that she is able to read within this strange landscape with its barns and islands and lingonberries the contradictions and disjunctures within her own personality. She is her mother’s daughter, you feel, even if she strives always for the approval of her father, who “rarely joins the cast of his family, but when he does, he has the air of a captain inspecting his troops”. The love the young Christina feels for her father is a complex, beautiful thing, the way she teases out his character a wonderfully subtle act of narrative control.

One of the conceits in the book is the juxtaposition of Christina’s everyday problems – with boys, with her adolescent faith, with jobs – and the increasingly horrifying position of her sister, who is gaining weight and losing consciousness on a host of medications. The strain on the family is clear, and Christina’s increasing religious fundamentalism is merely one sign of the toll that Caroline’s illness is taking on them all. Patterson lifts the desperate sadness of these passages with tender humour, poking fun at her own po-faced forays into evangelism and recording her sister’s obsessive love of the Romanovs. Caroline’s trip to Russia with her parents will have you punching the air for her, even as you recognise that there is tragedy ahead.

Patterson is brilliant on both physical and mental pain, and particularly on the linkages between the two. In one of the darkest passages in the book (and in her life), she is diagnosed with polyarthralgia, which, as she puts it, “really just means an awful lot of pain”. The pain is excruciating and without apparent cause, although the reader intuits that it is the physical manifestation of a deep unhappiness within. She goes to Sweden to join her parents on holiday and revisits the place where she was once so happy. “Back in the garden, staring out at the forest and listening to the grasshoppers, I wondered how someone who had so many friends, and such a loving family, could feel so alone.”

Little does she know how much more tragedy there is to come; indeed it seems that what brings her out of her slump is the collapse of everything around her, the sense of a ship going down with Patterson the only survivor. Everyone Christina loves dies, and dies too young. She is covered in acne, contracts lupus, is poleaxed by her debilitating and unexplained pain. She is adored by her colleagues at the Poetry Society and the Independent, but the men in her life treat her terribly. Just when there’s a break in the clouds and you think things might be working out for her, she’s diagnosed with an aggressive form of breast cancer.

And yet, despite it all, she survives, and more than that, she thrives. The final, joyful chapter looks forcefully ahead, ending with a wonderful passage of hope in the face of despair, a passage that feels like it is written just in case the reader feels any last shred of pity for her. She is on the verge of 60, and she is happy. “My cup runneth over,” she says. “I mean it. My cup runneth over. When the time comes, someone will have to wrest it [life] out of my hands.”

• Outside the Sky Is Blue by Christina Patterson is published by Tinder Press (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply