What would you do if you were a writer and knew you would be dead shortly because of cancer?

IN GRATITUDE

By Jenny Diski

250 pp. Bloomsbury. $26.

Jenny Diski was dying. It was 10:07 a.m. on April 25; I Googled to make sure, before I filed this review, that she was still alive. She was. Her “onc doc” gave her a year in April 2015, which meant, if she survived another seven days, she would technically beat the projections. She did not. She died on the morning of April 28, 2016.

Diski, as she makes vitally clear in her new memoir, “In Gratitude,” spent her every moment on earth beating the projections of authority figures. She overcame abusive and neglectful parents, foster homes, suicide attempts, repeated hospitalizations and the persistently gloomy conviction of relatives, caregivers, teachers, doctors and occasionally herself that she would fail at whatever she attempted.

Diski did not fail. Over the past 30 years, Diski published 17 books of fiction and nonfiction and became a writer who commanded descriptions from reviewers like “individual” and “wildly various”; her books — such as her 1997 “so-called travel book,” “Skating to Antarctica” (which she described as being about “Icebergs, mothers. That sort of thing”) — all proof, as Giles Harvey wrote in a 2015 New York Times Magazine profile, of her “spectacular originality.”

In September 2014, two months after the diagnosis, Diski began publishing essays in The London Review of Books about her illness and impending death. She was more than wary of the maudlin pitfalls (even she expressed disbelief at her choice to write “another [expletive] cancer diary”); as a result, her monthly testimonies are droll and uncertain and disobey time and, like memory itself, circle obsessively back to moments she finds most difficult to emotionally process, such as the realization that she will never see her small grandchildren “become their own people.”

Diski also began publishing essays about her quasi-adoption by (and subsequent decades-long relationship with) the Nobel Prize-winning writer Doris Lessing. “In Gratitude” collects like metal filings around these two magnetic points — the functional end of Diski’s life as a writer, and the functional beginning of it, due to Lessing’s “rush into kindness” and mentorship.

While her sections about cancer offer unruly testimonies to sickness and dying (and, frankly, living), it’s in the sections about Lessing where Diski’s idiosyncratic mind — and her bravery as a human confronting both imminent obliteration as well as certain vexing questions that, years later, she’s still rolling around in her head — is most potently on display.

Because of course the “in gratitude” of the book’s title contains, with one tap of the delete key, its negation. Diski riskily interrogates the ingratitude lurking beneath her feelings toward Lessing — the aristocratic savior (of the Communist-Sufi-literary variety) to her Dickensian waif. Diski was a classmate of Lessing’s son Peter, who urged his mother to invite Diski, 15 at the time and in a mental institution, to live with them.

Diski accepted Lessing’s invitation and was tossed into a stimulating melee of writers and activists (among those at the Lessing dinner table were Ted Hughes and R.D. Laing). Yet she struggled with “a substantial amount of anger at having to be grateful, the gratitude ever increasing, the bill never settled, and made more enraging by Doris’s insistence that I wasn’t to feel it.” Lessing, to her credit, practiced what she preached — just stop being emotional, she was known to advise. Also known about Lessing: She had left two young children in Southern Rhodesia when she moved to London with Peter to pursue her dream of becoming a writer.

“In Gratitude” stalks a particular early moment in Diski’s relationship with Lessing. Diski, who had been shunted between various institutions since birth, who knew too well “the fearful feeling of privation when your time as part of a system runs out,” was terrified of being kicked out of this new system as well. She bumblingly confronted Lessing one night: “I wanted to know if she liked me, and what on earth could be done if she didn’t.”

Lessing reacted badly. The next morning, Diski found a letter from Lessing, accusing her of emotional blackmail.

Diski is not condemning Lessing for her behavior. She is seeking, in these final moments of her own life, the fullest possible understanding of a woman who represented, despite her prickliness and remove, the closest thing she had to a family. Diski courageously and persistently speaks what many might deem unspeakable. She tries to comprehend Lessing’s ability to leave two children on a continent so far away she was guaranteed never to know or even much to see them. “I get the need to flee, but no matter how I try to put myself in her place, I am perplexed by her emotional ability actually to do it.”

But Diski always lets Lessing respond from the grave. To the contention that she, Diski, could never imagine leaving her own daughter in order to “fulfill her promise” — “Doris would say, I think, that I was lucky I didn’t have to.” Diski proves again and again her spectacular originality in her ability to empathize with as well as profess a total failure to comprehend the mind of another human being. These pages are evidence of her undiminished aptitude, even while her body was on the wane, to vigorously inhabit and investigate emotional spaces that shift and change shape as her sentences accrue.

While I couldn’t read “In Gratitude” without a persistent lump in my throat, and without the persistent awareness that its author was in a bed, somewhere, experiencing the very last days or hours or minutes of her life, Diski’s final book proves transcendently disobedient, the most existence-affirming and iconoclastic defense a writer could mount against her own extinction.

Heidi Julavits is the author, most recently, of “The Folded Clock.”