In 2008, Tom Lubbock, the Independent's chief art critic, was diagnosed with a brain tumor. In 2011, he died at age 53, leaving behind his wife, artist Marion Coutts, and their 3-year-old son. "The Iceberg" is Coutts' poignant and powerful account of Tom's last years and her struggle to stay afloat as her own life fell apart.

Coutts opens with the day she was told the devastating news, which "makes a rupture with what went before." Tom undergoes brain surgery and, after the worst possible biopsy results, starts a course of chemotherapy. Life goes on: Both adults work, share parental duties, take vacations. But at night, "insomnia rules the house."

Coutts buckles with the strain, aware she is "nearing the iceberg" and terrified of the greater pain lurking beneath: "the floating mass of ice that is still to come."

There are flickers of good news — positive scans, miracle drugs, hopeful oncologists — that give everyone "a rocket of energy like a burst of ticker tape, a firework display, a rain of glitter from heaven." But moments of relative calm are punctuated by fear, fatigue, infections and Tom's violent seizures; these moments come to a complete halt when the tumor grows, precipitating a second operation.

In time, Coutts is forced to accept an unpalatable truth. "There is going to be destruction: the obliteration of a person, his intellect, his experience and his agency. I am to watch it. This is my part."

Before that final destruction we behold Tom's slow deterioration and eventual journey from hospital to hospice. We read with grim fascination as he muddles his words or loses them completely. This affects his writing and dents his confidence, but the consequences go beyond work and also affect communication with his family, causing him to stumble through exchanges with his wife and bedtime stories with his son.

"The Iceberg," by Marion Coutts

Meanwhile, Coutts is introduced to a new, unspeakable vocabulary. "Carer is one I resist. Palliative another. Single parent — I never voice it but it is the case."

On its release in 2014, "The Iceberg" was lauded by the U.K. press and went on to win or be shortlisted for coveted nonfiction prizes. The acclaim is wholly justified. And yet there will quite rightly be skeptics. Why read a book so bleak, so dark — and, as a chronicle of a death foretold, so predictable? But like that other recent meditation on living with grief, Helen Macdonald's "H Is for Hawk," Coutts' memoir unfolds in the most breathtaking, heart-stopping prose.

She tells it like it is, brutally and unflinchingly, but her original thoughts, acute observations, candid feelings and brittle poetry combine to work wonders, compelling the reader to salute her and accompany her to the book's tragic end.

Coutts' last 10 pages could be the most moving you will encounter all year. We close her book and emerge stunned yet transformed from a singular reading experience.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the Daily Beast. He lives in Edinburgh, Scotland.