A man walks into a bar and, two years later, the bartender has a publishing deal. That’s how it went for Patrick deWitt and, three books later, this stroke of good fortune still unnerves him. “If I hadn’t gone into work that day or if that man had decided to drink somewhere else … There’s so much luck involved in anyone’s success. I’m sure I would have seen it through in some other way but you have to take a moment.”

That was in the middle of the last decade, since when DeWitt has become a successful full-time writer based in Portland, Oregon. His second novel, a first-person cowboy and gold rush story with a very clever title – The Sisters Brothers – was a huge hit. It was shortlisted for the 2011 Man Booker prize, and next year will be made into a film directed by Palme d’Or winner Jacques Audiard. I meet DeWitt a few weeks before publication of the keenly anticipated follow-up to his bestseller, the less catchy sounding Undermajordomo Minor, which DeWitt says could be thought of as the second part in a loose trilogy of adventures.

The book tells the story of Lucien Minor, known as “Lucy”, who leaves home at 17 and travels with a first-class train ticket to a job at the Castle Von Aux at the foot of a snow-covered mountain. There, as undermajordomo, he must wait on and assist the majordomo Mr Olderglough, do the shopping, avoid the demented Baron who prowls the castle at night, and start to realise his own thwarted personality and ambitions.

In the village he meets and falls in love with Klara, who unfortunately is already romantically entangled with a soldier. Between making cosy visits to her small family, fretting about his alarming rival, uncovering the mysterious fate of his predecessor, witnessing an aristocratic orgy and going about his daily business, Lucy becomes the hero of a grownup gothic fairytale that is recounted in a distinctive, mannered diction that will be familiar to readers of DeWitt’s previous novel – so the Baron waits for a train “on the appointed day and at the appointed hour”; thieves in the night are “an untoward happening”; Lucy’s feelings are a “cleaved combination of adoration and acrimony”.

If this sounds unnatural, it is. But that is the point of DeWitt’s prose, and particularly his dialogue, which is highly stylised for comic effect: he thinks the fact that The Sisters Brothers made readers laugh was the secret of its success.

He also talks in this way, using words like “avail”, “malady” and “departed” where others might say “help”, “illness” and “left”. While he cuts a thoroughly modern figure with his smart glasses, shirt, jeans and tattoos, his vocabulary is quaint, and this old-fashioned side of him also comes out in the way he writes about, or rather avoids, the subject of sex: “I am a bit prudish, I think. It’s hard for me to write about sex, and I don’t really care to read about it either. Maybe sex is more sacred to me than violence, which being raised in a society where violence is so prevalent I can approach in a very casual way.”

DeWitt, who turned 40 this year, is Canadian, born on Vancouver Island. The second of three brothers, he spent his childhood bouncing up and down the west coast of North America. He describes his father as “one of those people who never really recovered from having read Jack Kerouac’s On the Road”, and the family would move down to southern California only to realise they missed Canada and up sticks again.

The beat writer and poet Jack Kerouac in the 1950s. Photograph: Mondadori/Getty Images

His mother didn’t go to college and his father, who did, worked as a carpenter. DeWitt credits his father with having instilled in him a “lifelong interest in literature”, which was learned by example: after long days building houses, his father would come home and read on the couch. Both parents loved and encouraged music (country for her, jazz for him) and were eclectic readers, but their son never got on at school. His teachers, he says, were “embittered and disenchanted individuals who weren’t interested in the fact that I was reading books none of the other students were reading”. He reacted against the system, dropped out before graduating, and began drinking and taking drugs.

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The faded tattoo on his forearm is a lighthouse, a relic of a time when a lighthouse keeper was the only job he could think of that he might like to do: “Looking around I saw so many unhappy adults, people who loathed their jobs, and I didn’t want to be one of them.” His parents gave parties, mainly stayed out of politics, and focused on having a good time.

But amid what DeWitt looks back on as a typical phase of adolescent self-destructiveness and nihilism, a plan began to take shape, and in between working in kitchens and on building sites, he began to read more, studying the novels he liked to figure out how they worked, realising he needed to keep regular hours if he was going to get anything done, and starting to take himself seriously. Working in a bar three nights a week in his 20s, and after abandoning at least four previous attempts, he spent around a year writing a first novel pieced together from character impressions recorded on Post-it notes he stuffed in his pockets behind the bar and studied at home the morning after.

One night DeWitt asked a customer he knew slightly to look at the finished manuscript. This man, who was a screenwriter, liked it and passed it to another acquaintance, a musician, who had once been in a band with another man who was now a literary agent. DeWitt had married his girlfriend, had a baby son, and moved to Bainbridge Island, Washington state, by the time the agent called him.

I am a bit prudish, I think. It’s hard for me to write about sex, and I don’t really care to read about it either

That was how his career as a novelist started, and “the degree of luck involved in that story of those three people – the screenwriter, the musician and the agent – lining up like that makes me uncomfortable to this day because it seems so tenuous,” he says.

But discovered as he was against the odds, without a formal education and while selling drinks part-time, DeWitt’s first run of luck ran out pretty quickly. Almost no one bought the novel, Ablutions, despite enthusiastic reviews, and after a week his excitement evaporated.

Given an advance for a second attempt, he decided to try something different. That something, in a word, was plot: “Certain writers look down their noses at plot and I think I might have been one of them until I tried it,” he says, “but The Sisters Brothers changed me as a writer. I’m now operating with two goals in mind. One is to make a document that is beautifully constructed on a sense and word level, but I’m also interested in the compulsion to turn a page, to see what happens next. If these two things come together, that’s the ideal for me as a reader, so that’s what I’m shooting for.”

The English novelist Ivy Compton-Burnett is, unexpectedly, the first name DeWitt comes up with when asked about his literary influences, but his new novel’s biggest debts are to two European works of the 1970s: German director Werner Herzog’s film The Enigma of Kaspar Hauser and Czech writer Bohumil Hrabal’s novel I Serve the King of England. DeWitt reread this strange story, about a waiter buffeted by the terrible events of 20th-century history and thrust up against “the piggish impulses of the wealthy”, just before starting his third novel: “I have certain totem books that I think of as an ideal – they fill you with an energy and propel you to sit down and begin writing.”

While many authors seek inspiration from unusual sources, and have their own rituals surrounding the processes of reading and writing, DeWitt’s autodidacticism makes him highly unusual – particularly today, when so many American authors have studied creative writing (an academic discipline DeWitt didn’t know existed before being published). “I had a bit of a belligerent attitude towards the establishment,” he says, and while he can now see how a teacher or mentor could have been useful, he is proud to have managed without. The carpenter’s son regarded fiction as a craft he needed to study; his self-employed father was a role model who showed him how to work on his own.

Undermajordomo Minor by Patrick deWitt review – a comic tale with a touching protagonist Read more

DeWitt kept his writing secret, partly because he thought people discussing their dreams in Los Angeles bars were a sad cliche, and only after he was published did he begin to meet people who shared his interest in books. Most of his old friends are in either Alcoholics or Narcotics Anonymous. Knowing he did not want to give up drinking altogether, DeWitt found another route out of addiction and now drinks moderately: Portland, he says, has “excellent cocktails”. He is separated from his wife, but they remain on good terms and share the care of their 10-year-old son.

As well as his commitment to plot and idiosyncratic language, DeWitt has developed a particular interest in how character is expressed through dialogue: “You can show so much about a person from what he shares and obscures,” he says. “I come back more and more to the rhythm of conversation, when two people are engaged and feeding off one other, that is relentlessly interesting to me. I come by writing dialogue fairly naturally, I’ve got a chatty family, I’m a bit of a voyeur, and if I’m ever in a public place I automatically find myself listening.”

Having received mixed reviews, Undermajordomo Minor looks unlikely to repeat the extraordinary success of its predecessor, but DeWitt is enjoying himself and making plans. John C Reilly, who acted in the 2011 independent film Terri, based on a screenplay by DeWitt, bought the film rights to The Sisters Brothers and will star in the role of Eli, the more charismatic brother and the novel’s narrator. Meanwhile, DeWitt is keen to write more scripts and his next novel is already under way.

“If I think of myself as writing in any tradition, particularly with the last two books, it’s maybe a tradition of people who are interested in upsetting tradition, usurping a genre or even kicking it in the teeth,” he says. “I’m making it sound meaner than I feel in my heart – it’s a very youthful, gleeful feeling. Like drawing a moustache on a beautiful painting, there’s a touch of the vandal to it.”

• Undermajordomo Minor by Patrick deWitt is published by Granta. To order a copy for £10.39 (RRP £12.99) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.