Justin Cartwright's new novel begins with a bracingly unsentimental premise. After the death from cancer of Nancy, his wife of more than 30 years, David Cross feels not devastated, but released. "Without Nancy, he is both more uncertain and more free." She has brought up his children and kept a home for him to return to between adventures - he's a retired TV news reporter, who toured foreign wars and trouble hotspots - and outwardly he pays his dues of gratitude for that. No one else knows what he acknowledges to himself: how much compromise and falsity have been necessary to sustain their lifelong relationship. Among other concealments, he has never told Nancy that he knew about an affair she had when he was away and the children were small. Her death frees him to embark upon his new adventure of seeing things for what they really are, which is the story of the book. "After her affair, he found himself unable to see Nancy clearly. Now he feels he can inhabit her mind, as if he's moved into a vacated house."

It's not only David who is made queasy by the reality of married intimacy. His son Ed, 32, a solicitor, married to lovely ex-dancer Rosalie, "has intimations already - that marriage can impose a sort of heaviness that never lifts, a sort of muting of the senses". Rosalie desperately wants a baby. Ed is willing to want one too, to make her happy; but his private ironic vision of her character and desires doesn't bode well. "He knows how desperately she wants a little acolyte following her into the magical world of dance and he knows that she longs to dress her up for children's parties." The novel makes delicious short work of the domesticating pieties. Men feel penned inside the shelters women make. David has never liked the family home in Camden, Nancy's domain; he sees uniform brick boxes, individuated by touches of gentrification. His roots in London are in the old Soho of male camaraderie and bohemianism and illicit sexual frisson. Women spin "little myths around the family" to protect themselves from horror outside ("tsunami, earthquakes, murder, torture, betrayal"); "mothers lie on demand". Men in their sceptical truth-seeking disassemble the myths. Without Nancy's tending, the Camden house reveals itself as dingy and dated, and David longs to be rid of it.

When his daughter Lucy spends the night there, however, wearing one of her beloved mother's nighties, we see the home differently through her eyes: as a source of self, an enriching continuity. And through the twists of plot as the novel develops we understand that Ed's male sophisticated ironies won't necessarily overmaster Rosalie's female magical thinking. "She is a believer in moments - intense, meaningful, fateful, numinous, although he doubts if she knows the word". He may know the word, but it's Rosalie who makes the thing happen. She does get pregnant, in an act that takes a leap of faith, and imagination; her treachery is of a different order altogether from the ordinary kind Ed gets up to with the trainee in the office.

Retired, David has shed more than just his ill-fitting marriage. He's grown so thin, working out at the gym, that friends and family worry that he's ill. Cartwright dwells unmercifully on this time of reckoning, between a powerful man's prime and his decline. It isn't vanity, exactly, that drives David: he knows all about "his nipples obdurately puckered" and the "threads of grey hair on his chest". He's burdened by a lifetime's glib approximations, reporting to camera or reading from the autocue at Global television with "bogus gravitas", processing and packaging the suffering of the world for easy consumption. From underneath all this falsity, he needs to disinter what's true. Last reckonings beckon him, in the person of his eccentric, dying brother Guy, who's failed in everything - wives, children, career - but obstinately pursues transcendence in the Kalahari. Guy's a good invention, a flawed and obstinate prophet, sympathetic but comically inept.

How can David escape glibness, though, in this language of his inward narration - and of Ed's and Lucy's narrations too - which processes and packages unrelentingly? It is a problem that there's no difference between the novel's register of David's conventional fluency, and its register in the places where he's meant to come nearest to transcending that. In fact, whenever the language gets closest to a core of meaning, it tends to fall into quotation (from Camus, Kierkegaard, Wittgenstein, the Venerable Bede and others). These sublime imports, though, can't stop the hole; when David's at his most serious and trying hardest for the truth, he always sounds like the version of seriousness you get on the telly: speaking of "the never-ending and restless human desire to make some meaning out of life", or telling us that "under the Kalahari stars you see things differently".

 Tessa Hadley's Sunstroke and Other Stories is published by Vintage.

Justin Cartwright's novels tend to be satisfying explorations of acute dissatisfaction. His characters, nearly always middle class, are blighted by their expectations, undone by desire. The title of his recent novel, The Promise of Happiness, might have stood for all nine of his books. Though his characters would never be advised to hold their breath in expectation of contentment, it doesn't stop them trying. "And this may be one of the defining characteristics of our restless age," Cartwright writes in his latest novel, To Heaven by Water, "that all of us believe our lives could have been better or different."

The Cross family has been capsized by the sudden death of Nancy, wife to David, a recently retired newsreader, mother to Ed, a lawyer, and to Lucy, a curator. Nancy was the selfless matriarch who held together the competing egos of her household. Without her, the three survivors do not know which way to turn; they feel variously "more uncertain and more free".

David finds some refuge in old friends. The book opens with a sharp account of a regular Soho lunch which pins him exactly in a time and place: he is a child of the 60s, he worked in television in its innocence, "once Francis Bacon offered him a drink in the French House". Ed is in a life he is not sure he has chosen - a friend of his father's has taken him on in his legal practice, he is minting money, trying unsuccessfully for children with his ballet-besotted wife and feeling suddenly too grown-up. His sister, meanwhile, is trying to escape the attentions of an ex-boyfriend who is stalking her online.

It's an everyday tale of north London anxiety, then, punctuated by the inevitable soul-searching walks on Hampstead Heath. Except that Cartwright introduces a darker edge to his characters, in particular to David. He is troubled in his daydreams by the death of a former girlfriend, who drowned in a drunken accident; David knows he could have saved her, but ended up saving himself.

Cartwright adroitly manages this submerged guilt, refusing to let it overwhelm the novel, just as David has refused to let it overwhelm his life. It gets equal billing with the sense that the TV man's life never worked out as he hoped - David only accesses the guilt when he dwells on the time he believes he was happiest, on a film set with Richard Burton in Italy; he routinely measures what came later, his marriage, his kids, against that freedom.

In some ways, Cartwright sets David up as a test for his reader's sympathy. The character is damaged in some senses - vain, self-obsessed, duplicitous and, as we discover as the book presents its unlikely plot twist involving David and his daughter-in-law, capable of almost anything. But he is also charming, urbane, lived-in. We are asked to sympathise with him, to take him as an everyman, the avuncular prime-time anchor, comforting, even as he tells us the worst.

As David Cross is busy coming to terms with almost everything but the death of his wife, immersed in a late-life crisis that sees him favouring hippy T-shirts and Masai bracelets and a punishing gym routine, he also becomes an outlet for all Cartwright's world-weary observation. He turns over in his mind a critique of 24-hour news, the changing mores of eating out, the deceptions of memory and the consequences of fame; he habitually analyses political leaders - "There's a capacious, unused look to Gordon Brown," he'll think, "like a rectory with too many rooms. God knows what he looks like without his clothes on ... "

This carefully constructed consciousness, half the author's own voice, half his character's, is most effective with David, who is closest in age to Cartwright. The depictions of son and daughter are less complete and they come to life mostly in their father's presence. For all David's efforts at reinvention, he is resolutely a cliche in his children's eyes, the widower looking for one last sad go round: "Lucy lets herself into the house, which is acquiring a bachelor aroma of embrocation and fruit on the turn." David is less constricted in Cartwright's gaze, however. In the last quarter of this book, the author allows him a way out of the life he has made: he visits his long-lost brother, in the Kalahari desert and they share a kind of poetic catharsis.

This last section sometimes strains for closure, though Cartwright evokes the southern Africa of his childhood with a careful wonder. His writing is freed by the wide open spaces, just as his characters come to a closer understanding of themselves. There is always a neatness about Cartwright's novels - no loose ends - and this one is no exception; he answers the beginning's questions with the conclusion's logic, though there have been unexpected shifts along the way. It's not a morality tale; it refuses easy judgment beyond the one that Cartwright's characters would be advised to take very seriously indeed: be careful what you wish for.