In 1977, two years after coming through Stage IV breast cancer, Susan Sontag wrote "Illness as Metaphor," a brilliant and cogently argued polemic about the punitive or sentimental fantasies that certain diseases -- such as tuberculosis in the 19th century and cancer in the 20th -- attracted.

What particularly angered her was the suspicion, accepted by many patients themselves, that cancer was partly the result of psychological repression; one could blame the victim. In addition, she who trusted in reason scorned doctors' tendency to infantilize their patients, even to keep them in the dark about the nature of their illness.

In 1998, Sontag developed a uterine sarcoma and came through that, as well. In 2004, at age 70, she learned that she had myelodysplastic syndrome, a lethal form of blood cancer. Her son, David Rieff, was not at all surprised by her refusal to resign herself to death. She'd already beaten the odds twice and now began ferociously looking for information about treatments, demanding that her doctors try everything possible, even unproven experimental procedures.

"Swimming in a Sea of Death," Rieff's memoir of the last, excruciatingly painful months of his mother's life, is as riveting as it is unremittingly harrowing. In those months, Sontag swung between despair and stubborn hope. She interrogated the Internet and her doctors, emboldened by a lifelong certainty that information equals knowledge equals power. The irony isn't lost on Rieff that his mother, a resolute atheist, had an almost religious belief in the always onward and upward progress of scientific research. "Was it not ... magical thinking disguised as practical research ... on the false premise that with that information there would be something new and transformative that could be done?"

She made herself, her son and her friends walk an absurdly wobbling tightrope. She did not want bromides, consoling lies or blind hope; she wanted the truth. But she could not bear to hear a death sentence; anytime she looked directly at mortality, she came close to going insane. Her doctors and her retinue of companions, all of whom knew that death was imminent, had simultaneously to believe that she could live. So they cherry-picked the ominous statistics for promising news and found mandarin ways of changing the subject and not saying certain things.

Sontag had a tremendous appetite for life. She thought the world stupid and corrupt and likely to get worse, but she was avid for more experiences: more books to read and write, trips to take, concerts and plays and theater to take in, friends and lovers to spend time with. Her formidable intellect could probe any topic except that of her own extinction. Her faith in science was such, Rieff tells us, that she believed it would one day be able to vanquish death. And in her own case, was she not special, having survived two lethal cancers already and thus deserving of an exemption from dying?

Very much his mother's son, Rieff heaps scorn on those who romanticize agonizing illness. Whether the victim suffers well or badly, whether she endures stoically or angrily, whether suffering brings out the best or worst in the patient -- none of it has any meaning. A deficiency in the genes or in some chemical malfunction of the body is a random fate; you bear it however you can.

And he shares Sontag's anger at the military metaphors often used in delusional, triumphalist discussions of disease, particularly cancer. There's a war on, we are fighting the insidious enemy who has invaded us, we are perhaps turning the corner, and we are confident that we will win the war.

After her death, Rieff suffers survivor's guilt. Was he right to become complicit in her belief that a cure was possible, or was he cruelly "refilling the poisoned chalice of hope"? Was her faith in science a blessing or a curse? There's no end to rehashing what one should or could have done differently. And Rieff knows that there's no "closure," either -- no end to grieving for someone you loved.

There is, however, something liberating, like a cold wind, in his refusal to ascribe any meaning, uplifting or somehow instructive, in his mother's ordeal. We are thrown into life, I understand him to be saying, and we are pulled fast or slowly out of it. Both are dumb luck. Merit and meaning are what we try to make happen in between.

Brigitte Frase of Minneapolis also reviews books for the Los Angeles Times.