When the American academic and novelist John Edward Williams published his third novel, in 1965, it was greeted with a respectful, albeit muted, reception by the literary press.

The New York Times gave Stoner, the story of an ordinary American man making his way in the world, a favourable enough write-up, while The New Yorker mentioned it in worthy terms in its “briefly noted” column. No other waves were made. After selling a grand total of 2,000 copies, Stoner seemed to suffer the unenviable fate of being respectfully shelved as that “quiet American novel”.

Until now, that is. The “quiet” American classic has become something of a slow-burn sensation. Nearly two decades after its author’s death in 1994, Stoner is hitting Europe’s bestseller lists, and causing a stir in Britain and America. The unexpected and widespread reappraisal has earned the epithet “the Stoner phenomenon”.

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Since its low-key republication by Vintage Classics last year, which had no publicity budget behind it, Stoner has, rather like Fifty Shades of Grey and Harry Potter before it, become an astonishing word-of-mouth success. It has been a bestseller in the Netherlands for the past two months where it currently sits at No 2, just below Dan Brown’s Inferno, while it was one of Israel’s bestsellers last year and is also reaching bestselling lists in France, Spain and Italy.

Unostentatious in its brilliance, the novel was all but forgotten soon after its publication. Maybe its tone was simply out of kilter with the times –On the Road had been published eight years earlier and the Beat generation was still all the rage. Stoner’s brand of realism, it would seem, was just not fashionable.

“It was a forgotten novel by a forgotten man”, says Frances Macmillan, an editor at Vintage. “It’s not exactly the stuff of a commercial hit and in the cultural climate of the 1960s, it offered the opposite of sex and drugs and rock’n’roll. It’s about a [university] professor that the kids look at and say ‘we don’t want to be like that’.”

The novel’s hero, William Stoner, begins life on a farm but falls in love with literature and becomes an English literature professor at a Midwestern university – much like Williams himself, who was a novelist and university professor for most of his life (winning the National Book Award for his last novel, Augustus). Stoner’s career is largely uneventful, and his marriage is largely unhappy. That this is deliberately the story of an unremarkable man is stated in the opening lines: “William Stoner entered the University of Missouri as a freshman in the year 1910, at the age of nineteen. Eight years later, during the height of World War I, he received his Doctor of Philosophy degree and accepted an instructorship at the same University, where he taught until his death in 1956. He did not rise above the rank of assistant professor, and few students remembered him with any sharpness after they had taken his courses.”

Despite its seeming “smallness”, the novel is filled with life’s most profound moments and passions. Over the years, some have been perplexed by the book’s obscurity, given its literary excellence. CP Snow wrote about it the Financial Times in 1973, asking “why isn’t this book famous?” More recently, Patricia Reimann, from DTV – Stoner’s German publisher – described its subject matter as being the “final things of life. Love, commitment, compassion, work, backbone, truthfulness, death.”

Its first reissue by Vintage came in 2003, but few paid it any notice, so it became available only via print-on-demand. When it was republished in America in 2006 by the New York Review of Books Classics, writers including Nick Hornby and Colum McCann praised it, but it was only when it was brought out again last year by Vintage (part of a routine practice to “re-jacket” classic books) that word truly spread. There was an especially excited clamour after the bestselling French novelist Anna Gavalda decided to translate it. Since then, it has been reprinted 12 times, with sales rising from 300 copies a month to 6,000, with 110,000 sold in the Netherlands alone so far.

A host of novelists have now voiced their admiration. Last week, Bret Easton Ellis wrote in a tweet to his 412,000 followers: “In the middle of what might be one of the great unheralded 20th-century American novels: Stoner by John Williams. Almost perfect...” Julian Barnes is said to be a fan, as is Linda Grant; Geoff Dyer calls it a “beautiful and moving novel, as sweeping, intimate and mysterious as life itself”, while Adam Foulds says that it is “perfectly clear and solid, plainly present, and seemingly simple but it deepens like a coastal shelf”. The American novelist Chad Harbach says that he has “read few novels as deep and as clear” as this one.

While its success is belated, it is entirely well-deserved, says Macmillan. “It really is a novel like no other. It’s important to everyone who is reading it because it has at its heart the universal idea that every identity has a purpose, and every life has a value, however small it might seem from the outside.

“It is also about what books can do, and about the power of literature. The main character’s life is suddenly changed in an English literature class, and the book reflects the idea that a piece of literature or a poem can suddenly shed a light on your life.”

Vintage Classics is now including the first chapter of Stoner in the back of every eBook version of F Scott Fitzgerald’s The Great Gatsby – another novel that was originally published to poor sales. For Macmillan, the pairing of the two books is very apt indeed. “They were both misunderstood when they first went out, but they are both different versions of the American dream.”

‘Stoner’ by John Williams is out now, £8.99 (Vintage Classics)