Joan Didion's latest book, "Blue Nights," explores the death of her 39-year old adopted daughter Quintana. It's an event, “I hadn't dealt with it at any level, and I needed to,” she told WNYC's Leonard Lopate on Wednesday.

"Blue Nights" follows, and bookends, Didion's previous non-fiction work on loss, "The Year of Magical Thinking," which explored the death of her daughter and of her husband, John.

Didion told Lopate "The Year of Magical Thinking" wrote itself (she completed it in three months), but "Blue Nights" was not as easy to write.

“I’m not talking about it being easy because of the difficulty of the subject, or the sensitivity of the subject, I think it was a difficult book for me to write because it was an entirely different kind of book than I’ve ever written," said Didion. "It wasn’t a narrative, it was a reflection."

Didion and her late husband, John Gregory Dunne, adopted Quintana days after she was born, in 1966. Didion was 31, living in Santa Monica, and totally unprepared for motherhood.

"I didn’t have a clue what was involved," she admitted.

Quintana was diagnosed with a personality disorder and later had drinking problems. She also suffered from abandonment issues related to her adoption. Her death, unrelated to her mental issues, came after years of illness that culminated in septic shock and death from pneumonia.

The book starts with the first few words Didion wrote after her daughter died:

Life changes fast.

Life changes in the instant.

You sit down to dinner and life as you know it ends.

The question of self-pity.

Didion told New York Magazine that “the goal of the book was to get it off my mind,” but also to “bring it back.” She told Lopate that, “I don’t think there is any straightforward way to tell that story.”

Michiko Kakutani of The New York Times described the book as, “the work of a survivor trying to understand the daughter she has lost, even as she surveys the receding vistas of her own life, as age and illness and bereavement leave her feeling newly vulnerable and alone.”

Didion just turned 75, and has recently undergone physical therapy after falling down, but doesn’t spend much time thinking about aging.

“I never really thought about getting older, I saw myself through John’s eyes and he always saw me as younger,” she said.