“This was a much harder book to write than The Year of Magical Thinking,” says Joan Didion about Blue Nights. “With Magical Thinking, there was no place to go except where it went.”

Didion’s dreamlike, hyper-real account of the first year of widowhood “wrote itself,” she says. And what a book it was: Magical Thinking sold over a million print copies, won the National Book Award for nonfiction in 2005, and became a one-woman Broadway sensation starring Vanessa Redgrave from a script by the author.

Before Magical Thinking was published, Didion lost her only child, Quintana Roo Dunne Michael, then 39. Blue Nights began with Didion’s attempt to come to terms with the unbearable death of her daughter. It’s filled with “rosaries of neglects, derelictions, and delinquencies”—the self-recriminations of a childless mother reconsidering her history as a parent. “I realize now how much in a lot of little ways I had not given her [Quintana] credit for being as smart as she was,” says Didion. “I see her in a new light.” Halfway through Blue Nights, Didion put down the manuscript. “I called my agent, Lynn Nesbit, and told her I couldn’t finish it. I was going to tell Sonny Mehta. Lynn said, ‘Wait a while.’ ” Didion laughs. “So I did. Then I realized I had to finish it. I couldn’t not finish it.”

Didion also realized that the subject had changed; it had compounded. The book was not about the loss of a child per se but, as she writes, “this refusal even to engage in such contemplation, this failure to confront the certainties of aging, illness, death.” The heavyweight topic of Blue Nights is “this fear” taken on by a woman who looked death in the eye twice in 20 months, a writer who had navigated the cultural and political landscape of the last half of the 20th century and had deciphered the seismic shifts of our collective consciousness in essays, novels, screenplays, and nonfiction.

In the past 10 years, Didion has written with raw honesty not about the outside world but about her own interior geography. We Tell Ourselves Stories in Order to Live is Didion’s collected nonfiction (Everyman’s Library, 2006), and the title expresses her modus operandi for getting through the day. Telling herself stories—keeping alive what she has lost—Didion says, helps her “put my feet on the ground” each morning.

Didion always had great titles for her books: Play It As It Lays; Slouching Towards Bethlehem; The Last Thing He Wanted; and now, Blue Nights. “The moment when I felt it, when I had it, when I could do it [was] when I called it Blue Nights,” Didion says. “I wrote the prologue almost immediately after that.” The title refers to the summer twilight, when the elongated days start to turn a shade of blue that over a couple of hours deepens and brightens, then lingers, tempting you to believe that this time, just this once, night won’t fall. Blue nights are the metaphorical warning signs of inevitability: we get sick, we get old, we die. Our days end.

How did she come up with the title? “I really don’t know,” she says. “A couple of years ago... a movie... did you happen to see it... about Virginia Woolf?” (The movie is The Hours, adapted from the book of the same name by Michael Cunningham.) “Just the part where she was in the water was stuck in my mind. That was the gloaming.”

Blue Nights is the story of Quintana’s life, from her unexpected adoption to her troubled adolescence and young adulthood to her wedding and happy marriage and, finally, to her chain of illnesses and untimely death. It is also the unsparing account of Didion, how she missed the blue lights of her daughter’s problems, how she underestimated the joy, the pain, and the responsibility of being a parent. And, lastly, it is a delusional tale of a woman, Didion again, who neglected to notice that she was getting old, who thought she could write a different ending to life’s stories, whose brilliant mind, outsized talents, and successes provided no protection from life’s brutalities.

At 76, Didion is beautifully old, her highlighted gray bob freshly cut, her lips carefully lined and her nails manicured. She wears a blue and red–checked dress, a fraying red cardigan sweater, and sneakers. On Christmas Day 2003, Quintana was admitted with a life-threatening flu to Beth Israel North Hospital. Five days later, December 30, after Didion and Dunne returned from the ICU, Dunne suffered a fatal heart attack.

Quintana recovered slowly over the next few months through various hospital stays. That summer, she flew to L.A. with her husband, Gerry Michael, and upon landing, was taken to UCLA hospital with a cerebral hemorrhage. Didion reflects that before she got the news, “I had spent the day thinking I’d come out the other side”; then: “The doctors didn’t think she’d make it off the table.” Quintana survived the surgery, but died August 27, 2004.

Blue Nights begins on July 26, 2010, what would have been Quintana’s seventh wedding anniversary, and it recounts the picture-perfect ceremony at the Cathedral of St. John the Divine. The narrative then zigzags back and forth through Quintana’s life—and Didion’s.

Didion was an unconventional mother who came by the status unusually. She and Dunne got a call from a Beverly Hills obstetrician on March 3, l966, saying he had a baby girl for them. “I had been thinking about a baby for a while, but I hadn’t been thinking about bringing one home. They are forever. That seemed impossible that I would forever be responsible,” she recalls. The couple had met with the doctor a few months before, but “didn’t actually make a decision. We said call us, but I’m not sure.” There were no second thoughts when they saw the perfect baby with the “pink ribbon in the fierce dark hair.”

“Not that baby... that baby. The baby with the ribbon,” Didion writes of how Dunne would tell Quintana about the day they chose her. Dunne saw Quintana off to school in the morning, Didion tucked her in at night. Didion often read poetry to put Quintana to sleep. Once “Q” was asleep, Didion says, she would stay up late into the night and work, then read poetry before she went to sleep.

A framed copy of “The World,” a poem Quintana wrote when she was seven, hangs in Didion’s kitchen, printed carefully on construction paper:

The world/Has nothing/But morning/And Night/ It has no/Day or lunch/So this world/Is poor and desertid.

Quintana, Didion says, was preoccupied with dying, but she adds, “We lived always in sunny places.... it was hard to see the dark. I didn’t want to see it. I didn’t see any reason to see it.”

Didion was able to ignore other things as well. She says she wasn’t aware of getting old “until John [Dunne] died.” She refused to acknowledge her mother’s decline. She only wanted to see the lightness in her child, the beautiful baby, the young girl in her school uniform, the bride with flowers in her hair. All those Quintanas are there in the photographs in her living room, one a life-size poster.

Quintana’s look-alike sister tracked her down with a Fed-Ex letter in 1996. Quintana’s birth parents had married after they gave her up for adoption and then had two more children. Her biological mother called Quintana until, when Quintana asked her to give her a little time to get used to what she called “being found,” the mother disconnected her phone, saying she did not want to be a burden. Didion is sparing in the details of her daughter’s blood relatives, even kind. “I had a very strong feeling that this family had given me their child.”

When asked how she defines herself—a wife, a mother, a writer—Didion says she knew she was a good wife; she isn’t sure what kind of mother she was. “I used to say I was a writer, but it’s less up front now. Maybe because it didn’t help me.” She’s not sure whether she will write again, certainly not about the topics she took on in the 20th century. Writing about morality and culture is like “pushing the stone uphill again. You write about X political events and nothing happens. That doesn’t push you to write again.” She continues to read. There is a galley near her chair: Sherwin B. Nuland’s The Art of Aging. But she doesn’t read poetry any more. She goes to bed at 7:30 most nights, and gets up at 6 a.m. “In fact, I can hardly stay awake. I go to bed earlier and earlier for reasons that escape me. If I stay up any later, I’m ruined for the next day.” On this late August afternoon, the day before the anniversary of her daughter’s death, she says, “Of course, that’s going to change now that the light is changing.”

Carrie Tuhy, former editor of Real Simple, is cofounder of SecondLivesClub.blogspot.com.