So many identities, so little time! There’s a lot of breathless trying on in Zadie Smith’s first collection of short stories – as if she’s late to a fancy dress party but still can’t decide what costume to wear. Or whether to go in fancy dress at all. Or maybe go to the cinema instead? There is autofiction here, along with formal experimentation, dystopian sci-fi, surrealism, social satire, parable and a story from the point of view of God that reads like a droll reflection on creative restlessness.

“To me, it was beautiful to move between these parallel projects, never getting bogged down, not feeling defined by one way of doing things, feeling light, feeling free… Doesn’t mean it wasn’t avoidant behaviour,” says the omnipotent creator in Blocked.

Each of Smith’s five novels, from White Teeth (2000) to Swing Time (2016), have danced from one identity to the next, shifting accent, cadence, tone. Meanwhile, her protean essay collections, Changing My Mind (2009) and Feel Free (2018), have revealed a terror of intellectual calcification. Changing her mind is essentially how Smith feels free. But it’s also a trap. Even for a writer, Smith seems unusually anxious about time: wasting it, running out of it – or having it stolen from her. Time is freedom – to be curious. But aagh! Curiosity also takes a lot of time. Smith, now 43, suffers from a kind of intellectual Fomo, a rapacious interest in everything, which means just as she’s trying to knuckle down and focus, she’s giving herself more work.

The best stories here act as commentary on her fluctuations and doubts and blend her criticism with the energy and verve of her fiction

In Grand Union, the “parallel projects” proliferate. So, too, do her cultural references, from hip-hop duo Dead Prez to French poet and essayist Francis Ponge. There are 19 stories here, most set in the US (she teaches at New York University) and many of which ruminate on the conditions and attitudes that will best inspire creativity.

In Downtown, the narrator is an artist in New York who is visited by an artist who lives in a Hungarian forest. As he leaves her apartment, he says: “I don’t understand how you can live here, and be an artist, amongst all this social noise and all of these people.” The exchange sends the narrator into a “frenzy of self-hatred”. She wonders if it’s possible to live among the chaos of the city and be a “real artist”? Would a forest or even a jungle be more conducive? In its pace and its tangle of artistic and political angst, the tale is reminiscent of Olivia Laing’s short novel Crudo, only less batty and self-satisfied. Smith shows she can pull the same autofiction trick and be funnier and more knowing.

The writing in Grand Union is most alive when Smith is channelling versions of herself, that is, the storyteller (The Canker; Blocked), the teacher (Now More Than Ever), the mother (The Lazy River) or the bookish swot (Kelso Deconstructed). We find a combination of the last two in her best story, Sentimental Education, in which a harassed mum who is contemplating the menopause remembers her time at an Oxbridge college, where she and her boyfriend, Darryl, were among the few students of colour. His means of coping with the college’s cloistered privileged was to bring along his schoolfriend Leon, a cheerful, tracksuited petty criminal who dossed on his floor, charming his way into the affections of everyone from the cleaners to the posh totty.

It’s an intriguing tale of education, class, betrayal and sexual chemistry in which the female protagonist reflects on the ways in which she has objectified men: “There were people to whom you wanted to abase yourself, and people you wanted to abase; there were people you wanted to meet on a flat playing field – which was called ‘love’, for capitalism’s and convenience’s sake – and people you really didn’t know what to do with… wealth for somebody, but not her.”

This idea of inconsistency hangs over many of Smith’s stories. Is consistency important? Is it even possible? She is tacitly arguing a point that she has made more explicit in essays: that it is OK to change your mind.

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The inconsistency of quality is a more serious flaw. At least eight of the 19 stories in Grand Union aren’t very good. Two dystopian efforts, Meet the President! (a post-apocalyptic ramble about a child’s virtual reality game) and Escape from New York (inspired by the urban myth that Michael Jackson, Elizabeth Taylor and Marlon Brando fled the city together after 9/11), are cute ideas but on the page, both dawdle along. Her more conventional, naturalistic pieces, such as Big Week and Miss Adele Amidst the Corsets, are mannered and self-conscious; she struggles to locate the drama or interest.

The best stories here are those that act as commentary on her fluctuations and doubts, that blend her criticism with the energy and verve of her fiction. Smith has always been a bit of a smartarse and when she owns that smart-arsery, she’s not only incredibly funny but full of heart, wisdom and truth. At the end of Downtown, as the narrator gets ready for a night out in New York, she says: “I tried on four different outfits and then just went ahead and wore them all.”

• Grand Union by Zadie Smith is published by Hamish Hamilton (£20). To order a copy go to guardianbookshop.com or call 020-3176 3837. Free UK p&p over £15, online orders only. Phone orders min p&p of £1.99.