Josh Roiland teaches journalism at the University of Maine.

On a June afternoon in 1982, Joan Didion strolled through San Salvador’s Metrocenter Mall in search of water-purification tablets. The complex billed itself as “Central America’s Largest Shopping Mall,” and Didion took note of all its bourgeois trappings: designer blue jeans, foie gras, bar carts, expensive vodka. Outside, a three-year-old civil war seethed.

Didion had traveled to El Salvador with her husband, writer John Gregory Dunne, to report on the conflict for the New York Review of Books. The juxtaposition of conspicuous consumption inside and terror outside was typical of Didion’s illuminating journalism. But this time, apparently, she had had enough. “I realized that I was no longer much interested in this kind of irony,” she wrote in “Salvador.”

Finding no purification tablets, Didion left the Metrocenter and walked back to the Camino Real Hotel, where she and Dunne were staying. Waiting to cross the Boulevard de Los Heroes, she watched as militiamen jabbed guns into a civilian’s back and wrangled him into a van. Didion’s reaction: “I walked straight ahead, not wanting to see anything at all.”

Didion has tried to make sense of a troubled world through her prodigious output of journalism, essays, novels, screenplays and memoirs. As she told a University of California at Berkeley audience in 1975, “I write entirely to find out what I’m thinking, what I’m looking at, what I see and what it means.”

‘The Last Love Song: A Biography of Joan Didion’ by Tracy Daugherty (St. Martin's)

Tracy Daughtery captures Didion’s anxious journey in “The Last Love Song.” He guides readers through her desultory days growing up in the Sacramento River Valley, a childhood strongly influenced by World War II; her years at Berkeley in the 1950s, before the barricades; her loneliness in New York City, working at Vogue; her marriage to Dunne in the 1960s and her return to the Golden Land of California, where she became one the decade’s most insightful and provocative critics.

As writers associated with New Journalism, a form of narrative journalism that emerged in the ’60s, Didion and Dunne rose to celebrity. Daughtery takes us through boozy Hollywood dinner parties, book and movie deal negotiations, and the adoption of the couple’s daughter, Quintana Roo (named after a Mexican state on the Yucatan Peninsula). The author, a professor of English and creative writing at Oregon State University, then follows the family back to New York City in the late 1980s.

Daughtery captures Didion’s political transformation from a Goldwater libertarian (who deemed Richard Nixon “too liberal”) into something resembling a Democrat. Her writing changed, too, becoming more political. In New York, she lost her husband to a sudden heart attack at their dinner table in 2003 and her daughter just 20 months later, at the age of 39.

Now 80 and still living in Manhattan, Didion did not talk to Daughtery for this project; as he notes in the preface, “She leaves obvious potholes for a biographer.” Nonetheless, he accomplished the titanic task of reconstructing her life from her writing and interviews, all of which he sources in more than 100 pages of notes at the end of the book.

For readers who know Didion’s work well, “The Last Love Song” can be frustrating at times. Quotes pulled from sources years apart can seem out of context. For example, in describing their first California beach house, Daughtery offers a scene of the couple swimming in the Pacific Ocean with the adventurous Dunne yelling to cautious Didion: “Feel the swell! Go with the change!” While this scene is set in the mid-’60s, Didion didn’t write those words until after Dunne’s death, in her grieving remembrance, “The Year of Magical Thinking,” which won the 2005 National Book Award for Nonfiction.

The reader also must grapple with another constraint of Daughtery’s approach. If Didion didn’t explicitly write about a subject or discuss it in interviews, then it doesn’t appear prominently in the story. Her parents, for instance, such influential and tormented figures in her life, disappear for long stretches, as does Quintana. That said, Daughtery manages to tell a compelling story.

He ends his biography beautifully, recasting Didion’s haunting 2011 conversation with her friend and fellow writer Sara Davidson. Davidson tells her that writing about her late husband in “The Year of Magical Thinking” was a sign of strength. “I don’t call it strength,” Didion cautioned. “I call it pragmatism.” By then, after the death of her husband and her daughter, Didion had been shaken from her Western frontier ethic of toughness and self-reliance. As she told Davidson: “It’s not my code anymore.” She acknowledged that her new code would have to be rooted in acquiescence and acceptance.

“But I don’t mean giving up,” she said. “I mean . . . giving yourself over to what is.”

The Last Love Song
A Biography of Joan Didion

By Tracy Daugherty

St. Martin’s.
728 pp. $35