Lionel Shriver had long been struggling to match the impact of her 2003 school-shooting hit, We Need to Talk About Kevin. Then, four years ago, she put on a sombrero while telling an audience at a Brisbane literary festival that novelists should be free to portray whomever they damn well please, and to hell with ‘cultural appropriation’ (hence her woke-goading choice of headgear). Amid the fallout – someone walked out and wrote about it in The Guardian – Shriver got a second wind as a professional free-speech hawk; when she next visited Australia, it was at the invitation of a libertarian think-tank to reheat her views on identity politics in a talk later published under the headline ‘I’m sick of fighting moronic culture wars’.

Still, it’s a dirty job, and all that. The Motion of the Body Through Space, her new novel, is set in New York state and follows sixty-year-old voice-over artist Serenata, much in demand for her ability to mimic accents, regardless of class or ethnicity, until her clients in the audiobook and video game industries suddenly dry up on account of anxieties about, well, you probably guessed it. Someone tells her, ‘It’s got kinda not so great, for white readers of audiobooks to use accents. Especially of POCs.’ To add to her dawning sense of obsolescence, she’s a lifelong runner whose knees are giving way at just the moment that her husband, Remington, previously uninterested in her hobby, starts training for a marathon. Serenata’s wounded mockery of his new-found zeal fuels their marital aggro, which is intensified further when, ignoring a low-lying cardiac issue, Remington steps up his training regime under the supervision of a hot-bodied trainer who quickens more than his lap time.

So begins a knockabout skit portraying the fitness industry as a snake-oil scam seductive to young and old alike. Remington starts wearing purple Lycra, drinking ‘high-end sparkling water spiked with electrolytes’ and working out at home on a treadmill with surround sound and ‘a thirty-two-inch touch screen that virtual-realitied your progress over pastured hill and dale, replete with bleating sheep’. Serenata’s teenage Fitbit-wearing cleaner trains so hard to keep up with her glossy Instagram peers that her kidneys fail. ‘Bring out your best self, your true self, your über self,’ someone urges.

Behind this satire is the sense that Shriver is hunting bigger game: generation snowflake. Witness the metaphor that comes to hand when she describes Serenata’s joint pain, ‘sullen, glowering, like a disruptive activist who’d been asked to leave a lecture and had instead retreated resentfully to a back row’. When we learn that Remington’s exercise drive stems from his ignominious ousting from Albany’s Department of Transportation after an accusation of racially aggravated assault cooked up by his overpromoted boss, Lucinda, a younger black woman described as ‘a sexual harassment case waiting to happen’, it’s the point at which the novel switches into a jeremiad about how political correctness imperils the hard-won gains of the white American middle class.

Shriver expends a great deal of energy trying to persuade us that white men can be victims too, not least of careerist schemers out to game 21st-century anxieties about race, gender and sexuality. It’s potentially fertile ground, albeit tripwired with hazards, few of which she avoids. For a start, too much of the novel takes the form of what Serenata variously calls ‘urbane back-and-forth’ and ‘Noël-Coward banter’ with Remington over the puzzling gamut of millennial dos and don’ts, from gender-neutral pronouns to the permissibility of the word ‘wheelchair’ (‘Do you have to say “wheelchariot”? I have a hard time keeping up’). This isn’t low-hanging fruit so much as a sticky mess already swarmed over by a thousand op-ed columnists, including Shriver herself.

Remington’s career-ending outburst results from frustration that his thoughtful proposal for green, low-cost, publicly owned street lighting is being stonewalled by Lucinda, who has already bought a shipment of blue LEDs from China. At an employment tribunal he counters the accusation that he exploited his privilege as ‘an older straight white male who has attacked a young female-identifying person of color’ by pointing out that she’s the privately educated heiress to a Nigerian oil fortune. ‘My father was a construction worker, and my mother cleaned fish. Who’s really “privileged”?’ The trouble is, Shriver wastes the force of these digs at left-liberal complacency because she doesn’t know how to quit while she’s ahead: not only does Lucinda remove a memorial to a 19th-century philanthropist outed as a homophobe after the discovery of his letters in an archive, but she also changes a street named after an American president to Robert Mugabe Terrace. Shriver just can’t help lapsing into caricature: the chair at Remington’s employment tribunal announces that he’s ‘painfully aware of representing the white patriarchy. At least I identify as bi, so I have some sensitivity to the issues confronted by marginalized communities, by dint of my sharing the LGBTQIA space.’

At heart the novel is an essentially uncontroversial entreaty to avoid lazy thinking wrapped up in the story of a later-life couple rubbing along, in spite of their itchy (and blistered) feet. But instead of being zingy and scabrous, Shriver’s satire is so broad and so exaggerated that its impact is deadened. In the end, you’re left wondering why Shriver even went to the bother of reverse-engineering the scenario to make her point: it’s not as if she’s forced to resort to fiction for want of a public platform.