‘I am the sole author of the dictionary that defines me,” remarks someone on the radio at the beginning of Zadie Smith’s new novel, NW. Thirtysomething Leah, listening in her garden, tries to note this down, but finds she can’t write on her glossy magazine. Leah’s backyard summer reverie is about to be shattered by a distraught woman banging at her door, begging for help and money – and recognising Leah from their schooldays. Leah is conned into handing over 30 quid, thus providing a rare chance for her Irish mother and her black French husband to agree on something – her naivety. For NW, Smith returns to her old stomping ground of culturally mixed northwest London, the setting for her first novel, White Teeth (2000). Divided into several fragmented, stylistically disparate sections, NW centres on the long-time (but strained) friendship between two women, one white, one black. Leah and Natalie grew up in Caldwell, an impoverished housing estate where the tower-block lifts “were to be avoided almost as soon as they were built”.

Both have escaped, but to different degrees – Leah lives in a cramped council house and works at a community centre and Natalie is a well-heeled lawyer who shares an elegant Victorian home with her husband and children. Neither is really happy with her lot. The first section – a playful mix of styles that includes everything from stream-of-consciousness narration to text in the shape of a tree – focuses on Leah, her resistance to her husband’s desire for a child and the disruption set in motion by the conwoman Shar. The second is given over to Felix, a recovering drug addict whose eventual unhappy fate is already known to us. Next, 185 numbered and pithily titled vignettes lead briskly through Natalie’s life, beginning at age four, when she saved Leah from drowning, thus demonstrating the “celebrated will and foresight” that will lead her out of Caldwell, away from her family and on to greater things. (She changes her name from Keisha to Natalie, presumably in an attempt to appear less black.)

In the fourth section, a distressed Natalie returns to Caldwell and encounters a former schoolmate whose name, Nathan, echoes hers, but whose life has taken a very different route. Smith has described NW as a “black existential novel” (in the ethnic sense), and perhaps its subject is the choices people make, and to what degree these are constrained by class and ethnicity – how much anyone actually is the “sole author” of their life. The novel ends with Natalie and Leah puzzling over the nature of fate, the choices people make and the desperate lives of former contemporaries.

At her best, Smith is brilliant, witty and astute, with a fantastic ear for dialogue. NW is a terrific, multifaceted take on today’s London, and Smith is very good on the subtleties of human relationship, especially as inflected by class and race. The scenes where young Leah escapes her tense family life in Keisha’s larger, more expressive household – and, later, takes up clubbing, Ecstasy and lesbianism, while good-girl Keisha attends church and studies assiduously – are rich portraits of friendship and the tricky business of identity. But Smith has often seemed to struggle with endings, and NW is no exception. (She told the Telegraph she rewrote the last third of the book in several months after her husband criticised the original version.)

The final plot developments are set in motion by wildly improbable behaviour from Natalie, and the novel ends with a weak, poorly drawn scene that in no way matches its earlier flair and substance. So NW is both a brilliant novel and a flawed one – but one that is absolutely worth reading for its great characterisation, dazzling language and intelligence.

NW, by Zadie Smith (Hamish Hamilton, $37).

Caren Wilton is a Wellington writer.

BOOK CLUB

To join the conversation about nw, visit the book club section of www.listener.co.nz, follow @nzlbookclub on Twitter or go to the New Zealand Listener Book Club Facebook page. Next month’s Book Club choice is first-time novelist Alison Moore’s Man Booker Prize finalist The Lighthouse (Canongate, $24.99), which is released in New Zealand on October 1. Coverage begins in the magazine and online on Friday, October 5.