“When we read a book,” wrote Walter Benjamin, “the book is reading us.” I’ve been reading books by Joan Didion since the mid-’60s, and those books have been reading me, too. This, her latest, is a product of the twilight of her life, written in the aftermath of nearly unendurable losses. The back cover features a picture of her daughter, Quintana Roo Dunne, taken when she was, perhaps, 6 or 7 years old. That child was destined to die young, not long after her wedding, not long after her father, writer John Dunne, would die. Didion’s prose is as laden with imagery and detail as ever. Her style is both detached and intensely engaged. The tone she creates with that style “read” me from the very first time I read one of her essays. And because I assigned lots of those essays in classes I taught, I read them many times over, read them until I knew all her tropes—the rattlesnake in the grass, the photos of dead relatives, the chilly sense of dread she evoked. Those tropes all turn up here, too, devoted to her struggle to deal with the meaning of Quintana’s death, and the inevitable guilt that accompanies the loss of those we love. For such a slim volume, the weight of Blue Nights is nearly beyond lifting.