JOAN DIDION IS, AS WE KNOW, a cool customer. Long before The Year of Magical Thinking, in which a social worker calls her just that, we understood Didion to be cool in every sense of the word. Whatever was happening behind those bug-eyed sunglasses, within that frail frame, the author's relentless arrangement of information — the research, the reshuffling — kept hot feeling in line. This was true in Play It As It Lays, where the institutionalized Maria Wyeth's separation from her young daughter exists mostly between parentheses, and it was true in The Year of Magical Thinking, where the immediacy of loss is often cut with diagnostic material: W.H. Auden, observations about grief, and observations about those observations ("the question of self-pity") interceding before anyone gets wet. There is a moment in Blue Nights, in one sense The Year of Magical Thinking's logical extension but in another sense unlike any book in Didion's corpus, that seems to me specifically revealing: leaving a physical therapy session where she's been working out alongside members of the New York Yankees (!), Didion remarks upon her declining capacities. "My cognitive confidence seems to have vanished altogether," she writes. "Even the correct stance for telling you this, the ways to describe what is happening to me, the attitude, the tone, the very words, now elude my grasp."

"The correct stance?" It seems an odd thing to be fretting about in the midst of a meditation on aging and grief, but, in a way, Didion's entire body of work has been about this positioning: "the attitude, the tone." These things have always been primary in Didion — the words themselves have never been permitted to violate or distress the stance too much — which is frankly why a good portion of it doesn't interest me much. It's also why Blue Nights is so forceful. On the one hand, her cognitive confidence — or at least her cognitive capacity — is as powerful as it ever was. The book's surpassing lucidity (its title, seemingly generic, is in fact perfectly chosen, referring as it does to a specific set of latitudinal conditions in which "the actual light ... becomes more intense even as it darkens and fades, approximates finally the blue of the glass on a clear day at Chartres") owes much to the tension between that cognitive strength and the cracking, at last, of the writer's attitudes. Neither nakedly confessional nor coldly composed, Blue Nights is startling in its effect, and remarkable even within the context of Didion's impressive shelf. (Just because the work doesn't interest me doesn't mean I haven't read a lot of it, or that I don't think it's any good.) Blue Nights is heartbreaking, in a word, and if it isn't among her most exacting performances — in fact it contains a few moments of unusual clumsiness — it may yet be among her finest.

A word here about my own "stance," since it bears. During the years Didion lived in the house she refers to frequently herein as "Brentwood Place," my parents shared an employee with the Didion-Dunnes. The same woman who was folding Quintana's Westlake sweatshirts was also confronting the funky horror of my adolescent bedroom on a daily basis ("'Ordinary' childhoods in Los Angeles very often involve someone speaking Spanish," Didion notes, in a not-too-persuasive pushback against the notion that Quintana's upb...