If you threw a party for literature’s greatest detectives, from Sherlock Holmes to Easy Rawlins, it’s a safe bet that Inspector Jules Maigret would be far from the center of attention. Maigret, the star of 75 novels by the Belgian-born writer Georges Simenon, doesn’t perform flashy feats of deduction, wield the latest forensic gadgets, or chase criminal masterminds through waterfalls. He is a hulking, taciturn, middle-aged man who is almost always to be found either eating, drinking, or smoking his pipe. At night he sometimes goes to the movies with his wife, who after decades still calls him by his last name. He’d probably take one look around the party and slip away to his favorite bistro, the Brasserie Dauphine, just down the street from his office at Quai des Orfèvres, the headquarters of the Police Judiciaire.

So, what makes Maigret a favorite detective of so many literary writers and readers, from William Faulkner and André Gide in the 20th century to David Hare and John Banville today? The secret is that Maigret himself is almost a novelist—one who turns his gifts of imagination and empathy to solving crimes rather than writing books.

Naturally, Maigret has colleagues who do the usual detective things, like going on stakeouts and analyzing crime scenes, in order to bring him crucial pieces of evidence. But putting those pieces together means telling a story about the victim and the killer, and Maigret can’t do that until he knows them from the inside out: how they lived, what they feared and desired. “By the time all the characters had taken on the same human roundness, when he could ‘feel’ them … the mystery would be very close to being solved,” as Simenon writes in Maigret Gets Angry.

The original cover of La Pipe de Maigret, or “Maigret’s Pipe,” a collection of short stories published in 1947.

That moment usually comes about two-thirds of the way through the book, when Maigret will often take to his bed, or get drunk, or simply not respond when people talk to him. He is entering the same kind of trance state that made it possible for Simenon—who wrote some 400 books—to complete an entire novel in four or five days. This method produced books that are short—Simenon thought reading a Maigret should take no longer than seeing a play or movie—and simple—he estimated that he used a vocabulary of just 2,000 words. But within those constraints Simenon could produce endless variations, as similar and as different as Shakespeare’s sonnets or Monet’s haystacks.

Maigret himself is almost a novelist—one who turns his gifts of imagination and empathy to solving crimes rather than writing books.

It’s bittersweet news for addicts, then, that Penguin’s complete Maigret reissues came to an end this week, with the appearance of the 75th and final book, 1972’s Maigret and Monsieur Charles. This series of new translations in stylish trade paperbacks has been publishing about a book a month since 2013, in roughly the same order as the novels’ original publication. The new Penguin editions have sold more than one million copies worldwide, proving that almost half a century after his final adventure, the detective’s allure hasn’t faded.

Georges Simenon at dinner with Josephine Baker in 1920s Paris.

Maigret was never supposed to have such a long life. When Simenon came up with the character, in 1930, he intended to use him for a specific tactical purpose. As “Georges Sim,” Simenon had spent the previous decade churning out pulp fiction at an inhuman pace—in 1928 alone he published more than 40 books—and he earned a lot of money and a certain degree of fame doing it. But he dreamed of writing literary fiction, and Maigret was supposed to be a means to that end. The idea was to impress the public with the high quality of the Maigret books, produce a bunch of best-sellers quickly, and then move on to more respectable genres.

The first Maigret title, The Late Monsieur Gallet, was launched in 1931 with a big burst of publicity. Simenon’s publisher hosted a costume ball at a Montparnasse nightclub, where guests disguised as gangsters and prostitutes mingled with real Paris policemen. By the end of the year, 11 Maigret books had appeared. And right from the beginning, the detective was equipped with most of the traits that would define him for the next 40 years, most notably his reassuring size and solidity. “A hulk of a man, with shoulders so broad as to cast a wide shadow. When people bumped into him he stayed as firm as a brick wall,” Simenon writes in Pietr the Latvian.

Mentally and morally, Maigret is just as solid. He grew up in modest circumstances in the provinces and rose slowly through the ranks of the Police Judiciaire; he is a stranger to wealth and sophistication, and when he encounters them in his work they fail to impress him. His life is steadied by routine—above all, in his marriage to the indulgent Madame Maigret, who always has a delicious lunch waiting when he comes home from the office (though she often has to reheat it for dinner when he’s out on a case). In all these ways, Maigret is the direct opposite of his creator. Simenon famously boasted of having slept with 10,000 women (though his second wife, a skeptic, put the figure closer to 1,200), and he was perpetually on the move, traversing France on a canal boat or impulsively moving to Arizona.

Georges Simenon with Ingrid Bergman and Roberto Rossellini (at right) in Cannes, 1956.

In 1934, Simenon published the 19th Maigret novel, which was supposed to be the last. Titled simply Maigret, it ends with the detective retiring happily to the countryside. But eight years later, with France under German occupation, Simenon decided to bring back his most famous character for another outing, in Cecile Is Dead, simply ignoring the previous volume’s dénouement. Maigret was just what the war-burdened reading public needed—a “mender of destinies,” as Simenon describes him in one book. The occupation is never mentioned in Cecile Is Dead, but the book is nonetheless permeated by the guilt of a country torn between collaboration and resistance. For it turns out that Maigret himself is partly responsible for Cecile’s death: she was killed in the hallway outside his office after he kept her waiting for hours, thinking that she was just a lonely spinster with a persecution complex.

The new Penguin editions have sold more than one million copies worldwide, proving that almost half a century after his final adventure, the detective’s allure hasn’t faded.

From then on, Maigrets continued to appear steadily, two or three almost every year, until Simenon retired from writing, in the early 1970s. But part of the pleasure of the books is the way Maigret’s world barely changes, even as the world outside hurtles through history. Occupation and liberation, the Algerian crisis that brought France to the brink of civil war, the ascent of de Gaulle and the événements of 1968—through it all, Maigret keeps trundling from his apartment on Boulevard Richard-Lenoir, in the 11th Arrondissement, to Quai des Orfèvres and back again.

A scene from “Maigret et la Jeune Morte,” a TV adaptation of a Maigret novel that aired in 1973.

Simenon did make a few concessions to technological progress. At a certain point Mr. and Mrs. Maigret start watching TV instead of going to the cinema, and one of the last novels—Maigret and the Killer, from 1969—features a long-haired teenager whose hobby is recording strangers with a portable tape recorder. But even the last Maigrets feel closer to the 1930s, when the character was invented, than to our time—and that’s a large part of their allure. After all, who wants to live in a world where you can’t smoke in the office, a cop who drinks all day long gets sent to rehab, and DNA analysis solves more mysteries than empathy?

Adam Kirsch is a poet, critic, and editor based in New York whose books include Rocket and Lightship: Essays on Literature and Ideas