Into the chasm between commercial and literary fiction, a few genre-busting books occasionally fall. We are used to thinking of commercial novels as taking up all the prime real estate at Barnes & Noble and Borders, as being plot-driven and indifferent to the matter of prose style. Literary novels, on the other hand, tend to get stacked away in an oblique corner and are coveted — when and if they are — more for their perceptions and language than their story lines. The trouble is that only a minute portion of an already limited reading public actually buys them. And in a time of Oprah picks, as well as the blockbuster effect created by announced first printings of several hundred thousand copies, it’s increasingly rare that a small, shining gem of a book can rally the troops.

Sue Miller is one of those rare and lucky writers — Anne Tyler, Alice Munro, and Carol Shields are others — whose books cannot be dismissed as beach reads or airport fodder, despite their appeal among larger audiences. Ms. Miller’s subject has always been the demons that lurk within the heart of domesticity, the way families and marriages are soldered together and, under the pressures of time and stress, unlink. Ms. Miller’s first novel, the best-selling “The Good Mother” (1986), focused on the difficulty — and, finally, legal cost — of attempting to conduct a sexual life as a single mother. Her second-to-last novel, “Lost in the Forest” (2005), is a subtle, “Rashomon”-like accounting of a happy “blended” family — a mother, her second husband, two teenage daughters, and a 4-year-old son — living in the idyllic Napa Valley. The closer Ms. Miller brings them into view and dissects them by way of impinging tragedy, the more they begin to look like a family flooded with loss and pain, which has been kept under wraps by a certain willed certitude of outlook.

Perhaps because Ms. Miller came relatively late to writing (she was 43 when she published “The Good Mother”), she is possessed of an emotional maturity and earned, modest wisdom that is all too frequently absent from the work of younger, cheekier writers, many of whom — like the Jonathans Franzen, Lethem, and Foer — write out of a kind of skilled conjecture rather than felt experience. Although it is easy to dismiss Ms. Miller as a women’s writer mired in what might be called “kitchen issues,” she is ultimately intrigued by the encompassing subject of the hidden selves that lie behind our presented ones, the ways in which we build façades that either damage other people or create fissures within our own sensibilities.

“The Senator’s Wife,” Ms. Miller’s latest novel, already a best-seller, is a step forward for its author in its ambition, its scope, and in the fluency of its prose style. It tells a complicated, bifocal story, following the lives of two couples who happen to end up living next to each other in attached brick town houses, “with lots of white carved-stone trim around the windows and doors — curlicues and animal shapes. There’s even a small couchant lion at the top of the stone steps up to the porch.”

One half of the younger, recently-moved-in couple is 37-year-old Meri, an “almost pretty woman” whom a former lover described as “an attractive version of Pete Rose.” She comes from a difficult, lower-middle-class background in a small Illinois town (her father is a hard-drinking trucker and her mother is a seamstress) and has a leery attitude toward most things, having lived a “scratched-together life” before meeting her good-looking and charming husband. Nathan — who once “dazzled” Meri, and seems to go right on dazzling her throughout their marriage, his body reminding her of “an El Greco saint” — is an academic who comes from a more bourgeois and confidence-enhancing context than his wife’s:

Nathan has what Meri has come to think of as credentials: a distinguished, or at least a solidly reputable, academic for a father — long deceased — a mother who has a silver tea service, inherited from her parents … A mother who could say, when Meri admired it, ‘Oh, it’s just plate,’ as though that made it less remarkable.

The couple next door, long-established in the New England neighborhood of broad streets, chirping crickets, and yelping children, are an aging former senator named Tom Naughton, a charismatic figure in the mode of Kennedy or Clinton (Nathan is immediately interested when he hears the name of his neighbor-to-be), and his wife Delia, an elegant woman whose looks still speak for her: Delia is a deeply civilized woman who welcomes her new neighbors at once with a bottle of champagne and an assortment of gourmet nibbles — “a small circle of goat cheese, several pâtés, a baguette, a box of crackers, a jar of expensive mustard and some cornichons” — and offers to exchange visits. Meri becomes increasingly intrigued with the older woman and eventually discovers that the Naughtons’ union, which has produced three children, continues in name only, with occasional “ceremonial visits” from her husband. Throughout their marriage, Delia has endured a series of indiscreet infidelities, until Tom sleeps with her daughter’s friend, and Delia has finally had enough.

“The Senator’s Wife” is an elaborately strategized novel, with incident tumbling out after incident, which all the while manages to feel organically conceived. During the course of the year, Meri will become reluctantly pregnant (her ambivalence about pregnancy and about the pressures of being a new mother are some of the most compellingly rendered sections of the book) and happen upon the Naughtons’ secrets while house-sitting for Delia, who spends part of every year in Paris. Tom, incapacitated after a stroke, comes home to Delia, who defies her childrens’ collective disgust by agreeing to look after the errant spouse she still loves.

Sue Miller has always written a direct, unadorned prose and trafficked in insightful but not always surprising perceptions about the small fallibilities in human relations. Here, her language has turned elegant and precisely lyrical — Delia, upon seeing her aged and stricken husband undressed, is moved by “his skinny old body with the drooping dusky genitals, the pouches at his breasts” — and her observations unexpected. Meri, repulsed by her own pregnant state, thinks of other pregnant women she has known:

They’d all had to give up some sense of themselves as inviolably who they were, physically …. To learn to share their bodies with the stranger taking shape inside them. Why should she be any different? If her mother — mute, incapacitated before the complications of life — could manage this, surely she could.

Under cover of a conventional novel, in which C follows upon B follows upon A with several slight detours along the way, Sue Miller has fashioned a mesmerizing read — a consideration of the compromises inherent in old-fashioned marriages and the limitations contingent upon new-fashioned romances. She ignites even the most minor of characters with piquant details, and there is a sort of unassuming wisdom to the unfolding of this tale that is increasingly rare in contemporary fiction. “The Senator’s Wife” shows a master storyteller at her artful but un-selfconscious best — bringing us news of the ostensibly familiar world at home and, through it, the world beyond the home, where unknown anger and solace wait.

Ms. Merkin is a contributing writer to the New York Times magazine and the author of a novel, “Enchantment,” and a collection of essays, “Dreaming of Hitler.”