It was in 1929, while living on a canal boat in Paris, that journalist and short story writer Georges Simenon had the Eureka! moment which would help put him into the pantheon of crime fiction greats. It was a sunny morning, and the 26-year-old Belgian was enjoying a pick-me-up in a local café.

“I’d had one, two, maybe three small schnapps laced with a dash of bitters,” he later recalled. “In any case, an hour later, slightly sleepy, I began to imagine a large, powerfully built gentleman I thought would make a passable inspector. As the day wore on I added various accessories: a pipe, a bowler hat, a thick overcoat with a velvet collar. And since it was cold and damp on my abandoned barge, I put a cast-iron stove in his office.”

Fans of Inspector Jules Maigret will recognise that description of the character Simenon’s schnapps-inspired mirage turned into. He made his literary bow in 1931 in a novel titled Pietr The Latvian (as did his stove: it’s mentioned in the first sentence) and over the next four decades Simenon published 75 novels and 28 short stories featuring the hard-nosed Parisian detective. The series ended with Maigret And Monsieur Charles in 1972.

For that achievement alone, Simenon is worthy of respect. But the Maigret novels aren’t the whole story. In fact they’re only part of a much wider portfolio of work which stretches to around 150 novellas and 200 novels in Simenon’s own name, plus dozens more under various pseudonyms. And it’s here that you find the Belgian’s best work.

In 2014, Penguin embarked on an ambitious programme to publish virtually all of Simenon’s novels in new translations, including his non-Maigret work. The Mahé Circle, which had never been translated into English, was one of the earliest to see the light of day. The series is ongoing and in the autumn, Penguin will publish The Strangers In The House. Written in 1940, it’s the story of a drunken recluse in a rambling mansion who hears a gunshot one night, finds a body in a second-floor bedroom and has to decide what part in the death his estranged teenage daughter may have played. That will be followed early next year by The People Opposite, set on the Black Sea.

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Ahead of that, however, comes Betty. First published in 1961, it’s rare among Simenon’s oeuvre for having two female protagonists: Betty, a young woman who we first meet at the end of a three-day bender having dinner with a drug-addicted GP she has picked up in a bar somewhere, and Laure, older, wiser, wealthier (she’s widowed) and more sophisticated. She’s the lover of roguish adventurer Mario, owner of Le Trou, the restaurant in which the novel opens.

Laure takes Betty under her wing and installs her in the room next to hers in the plush Versailles hotel which is her home-from-home. There, Betty lies in bed and smokes, drinks, and reflects on the events which have caused her to walk out on her husband and children. Booze-addled and serially unfaithful, she’s a difficult character to like – but the agency Simenon gives her and the non-judgemental way he pushes her through the story make her irresistible too, even at the moment of betrayal which ends the novel.

Among the best of the rest of the non-Maigret novels – or romans durs, as they are known – are 1942’s The Widow, which explores the same themes as Albert Camus’s The Stranger (it was published in the same year and, much to Simenon’s chagrin, drew more acclaim); Three Bedrooms In Manhattan, from 1946; and Dirty Snow, published in 1948 and thought by many to be Simenon’s masterpiece.

It follows the short, brutal life of amoral 18-year-old Frank Friedmaier, a pimp and hustler in an unnamed city under occupation who kills a man for the hell of it as the novel opens and then wanders, emotionless, through a series of encounters with black marketeers, sex workers and various acquaintances (he has no friends) in the late-night bars he frequents. Comparing it to the work of noir great Raymond Chandler, American author William Vollmann writes: “Chandler’s novels are noir shot through with wistful luminescence; Simenon has concentrated noir into a darkness as solid and heavy as the interior of a dwarf star.” Come out the other side of Dirty Snow and it’s hard to argue with that description.

Three Bedrooms In Manhattan, meanwhile, details the frantic couplings and late-night, neon- and rain-drenched wanderings of an exiled French actor and the young, divorced mother he meets in a diner. Analysing its mood and construction, American novelist Joyce Carol Oates finds it typical of Simenon’s non-Maigret work: “a sequence of cinematic confrontations in which an individual – male, middle-aged, unwittingly trapped in his life – is catapulted into an extraordinary adventure that will leave him transformed, unless destroyed.” Among the artistic fellow travellers she cites are Camus, Marguerite Duras, radical experimentalist Alain Robbe-Grillet and the filmmakers Jean-Luc Godard and Alain Resnais, in particular their films À Bout De Souffle and Hiroshima, Mon Amour (which had a screenplay by Duras).

In fact, the love-in between Simenon and cinema is worth a novel in its own right. Wikipedia lists 46 big screen adaptations of his work. Betty was filmed by New Wave great Claude Chabrol in 1992, The Strangers In The House has had four big screen adaptations 50 years apart (James Mason, Geraldine Chaplin, Bobby Darin and Jean-Paul Belmondo all featured in one or other of them) and in 2007 Hungarian auteur Bela Tarr cast Tilda Swinton in a moody, black and white version of 1934’s The Man From London. Among the others are 1971’s The Widow, starring Alain Delon and the great Simone Signoret, and a 1965 version of Three Bedrooms In Manhattan by French cinematic great Marcel Carné. It features an uncredited appearance by a then-unknown American actor named Robert De Niro.

So, if your sense of the Maigret creator has been too coloured by cosy TV adaptations of his work – or, worse, you have conflated him with Agatha Christie’s pompous Belgian sleuth Hercule Poirot – then think again. When it comes to lifting up life’s stone, looking underneath and describing what he sees in economical prose and with a keen eye for every type of human frailty and depravity, there’s nobody like Georges Simenon.

Betty, Three Bedrooms In Manhattan and The Man From London are out now; The Strangers In The House is published on November 4 and The People Opposite on February 22 (all Penguin Classics, all £8.99)