NW is set in the same city as was White Teeth, the novel that made Zadie Smith famous in her early twenties. But while the characters in both books live in Smith’s native London, they occupy different universes.

White Teeth was replete with characters whose intersections were engineered for maximum impact: gung-ho Jehovah’s Witnesses, members of an end-of-the-world cult, cutting-edge geneticists, animal rights activists, and devotees of a radical Muslim brotherhood whose ridiculous acronym, KEVIN (for Keepers of the Eternal and Victorious Islamic Nation), seemed calculated chiefly to amuse, but toward what end it wasn’t clear. The story was full of punch lines and clever, manic plots that culminated in an epic clash at a press conference. White Teeth and Smith’s subsequent novels were often astonishingly observant about race, class, and the identity confusion that defines (or blurs) the lives of immigrants, but the characters remained, for all their color and verve, the playthings of her satirical wit. NW lies so far in the other direction that it resists being summarized at all. The climax isn’t a hyperkinetic denouement, but a foot journey through London one afternoon as two characters get high, reminisce, and recriminate. Yet NW, essentially a collection of character studies, accumulates enormous power.

In the northwest section of present-day London live four people who came of age in the fictional council estate of Caldwell, a section of government housing that is slowly giving way to private ownership. Leah, a one-time party girl of Irish heritage, works in a soul-sapping government office and tries to foil her West African husband’s efforts to get her pregnant. Felix, a former drug addict, is looking to turn the corner now that he’s found the right woman. Nathan, a thug who runs a panhandling and drug operation, was once a young boy with potential. And then there’s the one who made good, Natalie, who left behind what she viewed as the unserious name of her girlhood (Keisha) to become a lawyer and a wealthy man’s wife.

Smith’s skillful dissections of the societal tensions that hum through London will be familiar to readers of her other work. But the relentless excavation of her characters’ domestic lives feels new and startling. Describing a brunch at which two couples amiably chat about current events that don’t touch their lives in any way, Smith narrows the lens: “Only the private realm existed now. Work and home. Marriage and children. Now they only wanted to return to their own flats and live the real life of domestic conversation and television and baths and lunch and dinner. Brunch was outside the private realm, but not by much — it was just the other side of the border. But even brunch was too far from home. Brunch didn’t really exist.”

The most fascinating character in the book is Natalie Blake, one of that brunch foursome, who has become a barrister with lovely children, a lovely husband, and a lovely home. She’s grown distant from her family, ensconced in poverty and its attendant mindsets, and from her childhood friend Leah. In NW, gentrification is a thing that happens to individuals as well as to neighborhoods. And in both cases, the results aren’t always pretty. Smith’s intent isn’t to flay Natalie for acting white, though others lob the word “coconut” in her direction. Natalie is a hollow receptacle of achievement, and one of the things that Smith does brilliantly is to render that achievement both admirable and awful.

Natalie’s perfect-on-the-outside, inert-on-the-inside existence can’t be dismissed as simply bourgie because it’s hard to know what the alternative ought to be. Living knocked up in her childhood bedroom, like her older sister? Natalie knows that something is amiss. At times, she is reminiscent of the suicidal character in David Foster Wallace’s short story “Good Old Neon” who has known all his life that he’s a fraud. Natalie’s need to fill herself eventually drives her to do something inexplicable that puts at risk the life she has so consciously constructed.

NW is difficult to get into. Smith is playing with form and language more freely than she has in her other novels. The first section, which is devoted to Leah, is the most experimental, featuring stream-of-consciousness passages, fragmentary sentences, and squibs of dialogue that sometimes become unmoored from their speakers. These are admirable exercises but keep readers at a remove, exaggerating Leah’s dithering and aimlessness.

It’s only later, when Smith retraces the girlish friendship between Leah and Natalie (née Keisha), that Leah comes into sharper focus. The sometimes-whimsical, sometimes-loaded numbered subheadings that sprinkle this long central section frame revealing vignettes. “Permission to enter” heads a passage in which Keisha’s mother discovers a vibrator that Leah has given her. “And the scales fell from her eyes” titles a single paragraph in which Keisha’s hard-studying boyfriend dismisses Leah’s environmental activism as a “luxury.” “Some observations concerning television” describes a scene in which the successful, adult Natalie and her mother watch a reality television show about the poor that captures the chasm that has opened between them. Together these labeled fragments create a mosaic portrait of both Natalie and Leah while reminding us of the gaps between, of how much we don’t know about them.

White Teeth was a millennium baby. In the twelve years since its publication, Smith has written one largely forgettable novel (The Autograph Man) and one marvelous campus satire (On Beauty). She’s also become one of the best critics working today, producing literary, cultural, and film criticism that is incisive, skeptical, and generous all at once. Is she a better essayist than she is a novelist? Before reading NW, my answer was yes. Now she’s forcing us to evaluate her again, just as she has asked us to reevaluate everything from the varying vocal registers of Barack Obama to the role of Facebook in our lives. Unlike her early novels, her criticism exhibits an admirable restraint. Because she’s not spending all her time entrenching herself in a hard-and-fast position, she’s able to see around corners where others can’t. Given the evidence of NW, she’s a rare breed: a novelist whose work as a critic has improved her fiction. The result is this remarkable book.