“I have a slightly depressing theory,” the Irish writer Kevin Barry recently said. “If you look at any favorite novelist, the best novels are often number four, five, six. After that it tends to go into slow decline.” Happily then, he was discussing his fourth novel, “The Heart in Winter,” which was rapturously received when published in Britain and Ireland last month, and is being released in the United States on Tuesday. “Stop after six is my cunning plan!” he laughed.

He was speaking in his home, a picturesque, whitewashed cottage in rural County Sligo in the northwest of Ireland, where he lives with his wife, the academic and editor Olivia Smith. A pink yoga mat lay rolled up by the fireplace: Barry, 55, with a full beard and a wild head of thick reddish hair, practices daily. The house, he said, dates from the 1840s and was originally a Royal Irish Constabulary barracks. (The bathroom still has bars on the windows.) The couple moved into it in 2007, the same week Barry’s first book was released, a collection of stories titled “There Are Little Kingdoms,” which launched him in Ireland’s literary scene and won the prestigious Rooney Prize for Irish Literature. He has since written two further collections of stories and now four novels.

“The Heart in Winter” is a western and a love story, which would make it a departure for Barry if it weren’t for the fact that all his novels have been departures. “City of Bohane” (2011) is set in a gangster-run future Irish dystopia; “Beatlebone” (2015) is about John Lennon’s time on an Irish island he owned; “Night Boat to Tangier” (2019) is a Beckettian two-hander about drug dealers at a Spanish port. “I’m wary of repeating myself,” Barry said. “I’d be bored. And if I’m bored, it’s going to transmit.”

The new novel has, one way or another, taken Barry 25 years to write. He first had the idea for it when he traveled to the United States for a few weeks as a freelance reporter in 1999. (He showed me his recently rediscovered diary from the period, with “TO AMERICA!!!” scrawled across the top of one page.) One place he visited was Butte, Mont., by some reports the most Irish city in America — which gave him an idea for a book. “I’d received a royal welcome as a native Irishman. I remember sitting in the Capri Motel, with all this great material I’d been gathering about the bars and the brothels and the opium parlors, and the 10,000 Irish miners who had come over from west Cork. I started thinking, this is going to be gold … and it just wasn’t there.”

Barry explained his belief that “often, early on in a writing career, ambition and ability are in a difficult balance. You’re trying to write stuff you’re not ready for yet. When I started writing this in 1999, I thought: It has to be epic. I have to do the mines, I have to do the migration, I have to do the politics.” It was a case, Barry said, “of not knowing where the focus was. Usually it means you don’t have the right characters. And then those emerge 22 years later.”

The characters that emerged later (“What if it’s just a little story? What if they’re runaway lovers?” went his thinking) ended up being the center of “The Heart in Winter”: immigrant Irishman Tom Rourke and his lover, Polly Gillespie, who abandons her husband to be with Tom. Barry experimented with the characters for two weeks, trying to find their voices, and the book suddenly took flight. Tom and Polly steal some money and elope together on a journey west across 1890s America, pursued by the law, by Polly’s husband and by hired Cornish gunmen with names the reader can roll around in the mouth: Jago Marrak, Kitto Pengelly, Caden Spargo.

Earlier, Barry showed me the small space where he writes his books, detached from the main residence, situated next to his thriving vegetable garden (“Make sure you get that in”). The workspace is a long narrow room, no WiFi, no distractions, just a desk and chair with a rose gold MacBook, a couch, a dartboard and a speaker streaming choral music from his Spotify account.

Tom’s character came easily (“he’s a 29-year-old Irishman of literary ambition, so I know what that feels like”), but Barry was “nervous” about writing Polly, an American woman. Her voice is “very influenced by the Terrence Malick films ‘Badlands’ and ‘Days of Heaven,’ both of which use blankly poetic voice-overs.” Those examples were “like a tuning fork for Polly’s voice.”

Once he had the tone of the characters, “the romance felt real. [Tom] doesn’t know who he is. He’s trying on different personas. [Polly] is entirely certain of who she is.” Satisfied that the book would work, he spent a happy 10 months completing it, and “I was so pleased to finally get it out, I was seriously tempted to dedicate the book to myself.” (His wife — the ultimate dedicatee — had to talk him out of this.)

Barry — who refers to himself as “old-fashioned”; “I was never at a writing workshop in my life, I don’t teach” — has always been a voice-based writer. His style, fully formed from the publication of his first book at the age of 38, followed no particular Irish tradition, though it had a loose progenitor in the “bog gothic” of Patrick McCabe. His stories, regularly published in the New Yorker, are scabrous, grotesque and funny, in the kind of register that describes a hot day by saying, “Dogs didn’t know what had hit them.”

He now alternates novels with collections of stories, the short form remaining important to him. “If you have congenital impatience, as I do,” he said, “the idea of having a finished thing on your desk inside a relatively quick period of time is very attractive.” His work is characterized by punchy dialogue and a blend of cool satire and open emotion that at times recalls George Saunders.

“I’m fundamentally a comic writer,” he said. “Because if you can get them laughing, you can really go in then with the heavier stuff and the darker stuff and the moving stuff.” Certainly, “The Heart in Winter” takes the reader’s heart and wrings it out by the end. (Barry’s precise control of his style extends to recording his own audiobooks: “Trained actors,” he laughs, pulling a face at the phrase, “are not allowed!”)

Still, his writing has developed since the early stories. “I’m devoted to language and style, [but] I can definitely see a change over the last few books where my primary preoccupation is with the characters. I reside with them in a full-time way. And I miss them when they’re gone.” I suggested that “The Heart in Winter” is his most plotted novel. “The genre is very forgiving in terms of plot,” he said. “In westerns, people have to be constantly jumping up on horses and lighting out.” The tension builds, but never without comedy. One sheriff on Tom’s trail growls: “The best part of Thomas Rourke dribbled down his father’s good leg.”

Also, like all Barry’s novels, it’s a relatively short book: around 45,000 words. “And I’ve ambitions to get them shorter,” he said. “I love the idea of the three-hour novel. There are so many distractions in the world.” It’s a strategy for self-preservation, he explained. When he does literary events, the audience is “mid-50s up. Older readers are sustaining [the culture of readings]. I find the young people showing up at events are almost exclusively people trying to write stuff themselves. In 20 years’ time, this whole edifice could crumble.”

The answer, Barry concluded, was “to remove as much of the traditional furniture of the novel as possible. To strip it right down, and make the scenes really intense, and just place the reader there. And you’re in. And you’re not going to get out until you turn the last page.”

John Self is a book critic. He lives in Northern Ireland.