Paul Kalanithi was halfway through his neurosurgery residency when he began to work with a neurobiology professor. One day the professor, "V," confided in Kalanithi that he had been recently diagnosed with pancreatic cancer. After asking Kalanithi for his opinion on the symptoms and the course of treatment, V asked, "Do you think my life has meaning? Did I make the right choices?"

"It was stunning," wrote Kalanithi. "Even someone I considered a moral exemplar had these questions in the face of mortality." Not long afterward, Kalanithi faced his own mortality when physical symptoms that he attributed to a time-consuming, stressful job turned out to be the result of cancer that had spread throughout his lungs.

Cancer took Kalanithi's life last year at age 37, but not before he had the chance to write the majority of his memoir, "When Breath Becomes Air." With a foreword by fellow physician/author Abraham Verghese ("Cutting for Stone") and an epilogue by Kalanithi's widow, Lucy Kalanithi, his story is bookended by one who knew him by his work and another who knew his innermost self.

As a child, Kalanithi never imagined that he would become a doctor like his father, and he lost himself in the books of great authors that his mother introduced to him. He studied English literature and human biology at Stanford, but post-university, he says, he didn't "quite fit in an English department" and started his long road to becoming a neurosurgical chief resident.

It was at this point, the pinnacle of his career, that his cancer was diagnosed, receded and then returned to claim his life. When Kalanithi could no longer physically practice medicine, he found solace in writing and literature.

Kalanithi wrote an op-ed piece for the New York Times, "How Long Have I Got Left?" in January 2014, detailing his experience as first a doctor, then a patient, which grew into the memoir he left behind, its publication entrusted to his family.

As anyone who has worn a paper robe can attest, the roles of doctor and patient are clearly defined. What Kalanithi does in "When Breath Becomes Air" is interweave these two roles into one narrative.

As a doctor, Kalanithi has worked hard to keep mortality at a distance: As a cancer patient with a terminal prognosis "coming in such close contact with my own mortality had changed both nothing and everything. … The fact of death is unsettling. Yet there is no other way to live."

Meganne Fabrega is a member of the National Book Critics Circle.