Ben Markovits’s 12th novel opens with a confession. Its narrator, Tom Layward, a law professor, husband and father, tells us: “When our son was 12 years old, my wife had an affair…” Tom makes a private pact to endure his marriage only until their six-year-old daughter, Miriam, leaves for college. It is a quiet, bitter calculus, the sort of grimly rationalised fatalism that pervades the book. “What we obviously had, even when things smoothed over, was a C-minus marriage,” Tom reflects, “which makes it pretty hard to score much higher than a B overall on the rest of your life.” Markovits is an artist of such scorching recognitions – wry, unsentimental summations that make you wince at their truth.

Then, with the turn of a paragraph, 12 years evaporate. Miriam is 18, the family is summering at her mother’s parents’ house in Cape Cod, and Tom’s long-planned departure hangs over the novel like an unbroken storm. Markovits is superb at conjuring the temperature of a failing marriage – not through eruptions, but through the long accumulation of slights, hesitations and rehearsed hostilities. Tom’s wife, Amy, is masterfully drawn: brittle, commanding, a woman who has long since learned the tactical advantages of exasperation. The novel’s brilliance lies in how it refuses to reduce her to an antagonist – because, of course, Tom is just as complicit.

Yet Tom has more than just his marriage to reckon with. He is besieged – by the lingering, shifting symptoms of what appears to be long Covid (“palpitations, sudden fatigue… I woke up with a swollen face and leaky eyes”), by a professional implosion at his unnamed university, where his refusal to include pronouns in his email signature has made him a lightning rod for campus politics. Worse, he has provided legal counsel to the owner of a basketball team accused of racism and sexism. He is, in short, on the losing end of a culture war battle he has neither the stomach nor the conviction to fight.

With all of this in the air, he and Miriam set off to drive her to college in Pittsburgh. After dropping her, and seemingly on a whim, Tom just keeps on driving. His ostensible destination is California, where his son, Michael, is studying, but the journey is less a road trip than an act of attrition. He drifts through the wreckage of his past, stopping to visit old lovers, old friends, a brother, a business associate who ropes him into yet another consulting job in the ongoing ideological skirmishes of the NBA. If the great American road novel has traditionally been a narrative of youth – of possibility, of the US as something to be sought – then The Rest of Our Lives is its weary, middle-aged inversion. Tom is not discovering the US; he is retreating into it, moving not toward freedom but toward the inescapability of consequence.

Hemingway said he wrote best about Michigan when he was in Paris. Markovits, too, has spent much of his life outside the US – he played professional basketball in Germany, and now teaches at Royal Holloway, University of London – but remains one of the most astute novelists of modern America. The Rest of Our Lives is another quiet triumph, an elegant, devastating book that lays bare the way time calcifies our failures, how we find ourselves trapped not by circumstance but by the slow erosion of the will to escape. Markovits has long been one of our most under-appreciated novelists; this is yet more proof that he deserves far greater recognition.

• The Rest of Our Lives by Ben Markovits is published by Faber (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply