Matthew Thomas’s realist epic, “We Are Not Ourselves,” exceeds the usual boundaries of fiction on the subject. Tracking one family through three generations, it has a “Buddenbrooks”-like quality, offering a vision of a society in flux that is at once expansive and tangibly detailed. While Alzheimer’s disease comes to occupy the agonizing center of the novel, the word “Alzheimer’s” doesn’t appear until halfway through the book’s six hundred and twenty pages. “We Are Not Ourselves” opens with a series of resonant, finely observed vignettes, vital moments in the young life of Eileen Tumulty, a child born to an Irish family in Queens in the years after the Second World War. Burdened with alcoholic, financially struggling parents, Eileen is a shy girl who “would have chosen, of all powers, the power to be invisible.” But she harbors the usual outer-borough dream of social advancement. Standing outside a department store at Christmastime, Eileen longs “to be in one of those scenes in the window, frozen in time, in the faultless harmony of parts working in concert.” She thinks she has found that faultlessness in a charming young professor of neuroscience named Ed Leary; she imagines spending her life “tuning into the calming frequency of his thoughts.” As the years pass and the transmission between husband and wife grows increasingly garbled, this novel’s form—its simple chronology and the careful intimacy of Thomas’s prose—proves to be the ideal vehicle for conveying the insidious onset of Alzheimer’s. Ed, who has not missed a day of work “in twenty years,” tries to soothe his “cloudy head” by clamping on heavy headphones and listening to classical music in the living room for days on end. Eileen dismisses his early symptoms as a “midlife crisis,” but they worsen. Ed spends whole nights struggling to tabulate his students’ grades; he is injured when “his hand [is] no longer as fast as his mind”; this deeply “sensitive” man calls his wife a “bitch.” Ed’s strange behavior accumulates across nearly two hundred pages, until, at last, Eileen has the grim epiphany that Ed might be suffering from Alzheimer’s: “The dawning came all at once, though it felt as if it had been heading her way for a while, like a train she’d heard whistle from miles off that was now flying past and kicking up a terrible wind.” The fact that Thomas delays introduction of the book’s primary subject becomes crucial to its depiction. Before Ed’s diagnosis, we encountered him as a full and complex character—“open-minded,” “polite,” someone who “soaked up whatever you gave him” but is also “committed to his own pointless suffering.” By portraying the entire span of Ed’s adult life, Thomas frames Ed’s Alzheimer’s as a life-altering event but not as an occasion for a journey into the past. In this novel’s unswerving linearity, the past remains past, and Ed’s wife and son must reckon with a radically altered future. “Why Ed? Why now?” Eileen asks herself. “It hadn’t happened for a reason,” she decides, “but they would find something to glean from it anyway.” Thomas does not seek comfort in an imagined, wishful notion of a “wholly whole” Ed trapped behind his symptoms. The story is limited to the perspectives of Ed’s witnesses—later chapters alternate between Eileen and their son, Connell—and Thomas leaves it up to them to do that gleaning. The pages that follow offer the truest and most harrowing account of a descent into dementia that I have ever read. These are mostly intimate, domestic scenes, but Thomas understands how the numbing, repetitive minutiae of caretaking are often freighted with unspeakable pain. Eileen’s attempt to persuade Ed to lift a leg becomes a desperate struggle, her worry growing so severe that she implores God to tell her what to do. When Connell tries to help his father shower after an accident, the scene is an affecting display of a son’s love and a father’s remorse: Connell must clean his father but also attempt to spare him “great indignity,” as Ed flails “like a man on fire,” his “chest heav[ing] in deep, mournful sighs.” But for all the daily burdens of caretaking, the deepest horror is in Eileen and Connell’s contemplation of what is left of the Ed they knew. Not long after Ed’s diagnosis, Eileen grasps that “his real self wasn’t hiding in there waiting to be sprung. . . . [T]his was his real self now.” But Ed’s Alzheimer’s, like any, is vexingly erratic. The old Ed still vibrates into view for a few alluring seconds. “Something deep in him was surfacing,” Eileen briefly believes, “some essential fiber in his character. Then he stopped again.” It is that same dimming faith that inspires Connell, late in Ed’s disease, to spring Ed from his nursing home to enjoy one last Christmas at home. Ed’s drooling, babbling presence only reminds Eileen and Connell of how horribly “far” they have come, and Connell is seized with “an agony of regret.” Later, Connell looks at the lights strung up outside their home and thinks of happier Christmases, “trying to derive a simple pleasure from the lights, trying to forget that they and the hundreds more inside had not prevented the encroaching of a fathomless darkness. His father was gone, gone.” But this grim understanding brings Connell a degree of solace. He finds comfort, finally, not in the belief that there is a soul-like self trapped in his father’s addled brain but in the memory of the person Ed was before. “The understanding between us goes beyond words,” an earlier Ed writes, in a letter that Connell later opens, “and it is there that I live most fully, there and in the mental space I inhabit with your mother.” While this marvelous novel resists a glibly humanizing attempt to imagine what lies “beyond words,” the need to imagine remains. For all its insight, Thomas’s novel ends with the old question unanswered. If “we are not ourselves” in the depths of Alzheimer’s, who are we? After experiencing his own “sensation of panicked blankness,” Connell considers the possibility that he might inherit the disease, and he reassures himself with thoughts of the sensual joys that even Alzheimer’s can’t claim, pleasures that lie outside of selfhood: “the mouth-fullness of cannoli cream . . . the comfort of a body squeezed against one’s own.” This might be poor compensation, but it is one that I, too, try to believe in. Who knows? Perhaps, after the horror of memory loss passes, there might really be some relief in relinquishing your self and returning to the endless present in which an infant lives. Perhaps late-stage Alzheimer’s is simply unimaginable to those not afflicted with it. Perhaps it is incompatible with language, a place “beyond words.” The New Yorker