In 1991, in Sweden, Henning Mankell published a novel about a police inspector in the town of Ystad, in the southernmost region of the country. Mankell, born in Stockholm in 1948, had already published a half-dozen novels and had a number of plays to his credit as well. For some years he had divided his time between Sweden and Maputo, Mozambique, where he was a theater director.

The book Mankell published in 1991 changed the course of his life. Faceless Killers (as it was titled in the translation published in the United States in 1997) centered on Kurt Wallander, a fortyish police detective, and the team of colleagues who work with him. A police procedural with literary flair, the novel recalled the ambitious crime fiction of the husband-and-wife team Per Wahlöö and Maj Sjöwall, who collaborated on a series of ten novels published between 1965 and 1975. And like Sjöwall and Wahlöö’s protagonist, Martin Beck, Wallander was very much an everyman: divorced, a bit overweight, prone to drink too much, lacking political savvy, and fallible in many other ways, yet also (again, like Martin Beck) an extraordinarily resourceful investigator and a compassionate, deeply sympathetic man.

It wasn’t surprising, then, that Faceless Killers turned out to be the first book in a series, which—like the novels of Sjöwall and Wahlöö—combined storytelling and social commentary. What couldn’t have been predicted was the international success of the Wallander books—making Mankell famous, and launching the utterly improbable boom of Scandinavian crime fiction—and the extent to which Kurt Wallander would join the charmed circle of those literary characters who seem to take on a life of their own. There were eight Wallander novels—the last of these, Firewall, was published in Swedish in 1998—followed by a book of stories, The Pyramid, that served as a prequel to the series. Wallander also appeared in a couple of novels that featured his daughter, Linda, who had joined the police force. But for the most part, in the decade that followed Mankell concentrated on other projects: stand-alone novels, fiction for kids, plays, and a “book of memories” compiled with African parents suffering from AIDS, for their children to read when they are older.

Now, with The Troubled Man, first published in Sweden in 2009, Mankell returns to the Wallander series and brings it to a close. Even if there won’t be midnight vigils at which the faithful appear dressed as characters from the saga, this is an event for readers around the world. How will the story end?

What gives the question added force, especially for readers of a certain age, is that in the course of the series Wallander himself ages—like many of his American and British counterparts today, Ian Rankin’s John Rebus for one, but in marked contrast to the typical fictional detectives of the past—and undergoes the changes wrought by time. This opportunity to follow a character in time is one of the greatest strengths of contemporary crime fiction.

Here I must issue a warning: If you haven’t yet read this book and think you might, you should stop reading now.

Wallander’s nemesis is not an arch-villain along the lines of Erik Westin, the leader of an apocalyptic Christian cult with whom Wallander and his daughter tangle in Mankell’s post-9/11 novel Before the Frost, or the heartless magnate whose machinations Wallander slowly uncovers in The Man Who Smiled. What brings Kurt Wallander down is Alzheimer’s disease.

We have been prepared for this, unwittingly, by earlier books in the series that traced the deterioration of Wallander’s stubbornly eccentric father, a painter of workmanlike kitsch. Now we watch as Wallander’s mind unravels, from sudden memory lapses early in the book to the blankness of severe dementia at the end. He has rejoiced in the birth of Linda’s daughter, Klara. And yet in the epilogue, when his granddaughter comes running toward him, he is terrified by the realization that he doesn’t recognize the little girl: “He knew he’d seen her before, but what her name was or what she was doing in his house he had no idea.”

Along the way, struggling with his increasingly unreliable memory and a growing sense of disorientation, Wallander solves his last case. The details are convoluted, but the gist of it is quite clear, neatly summarized in this exchange of dialogue between Wallander and a Latvian woman he has loved, Baiba (she speaks first, and Wallander responds):

“Even in the Baltic countries, the way the Russians thought was dictated by what the U.S.A. was doing.”

“So behind every Russian was an American?”

In short (though the exposition of this point in the book is actually quite drawn out), the Cold War was really driven by the United States, and even today, to cover up the true role of America during the Cold War era (in supposedly neutral Sweden, say), it may be necessary to commit murder.

I must admit that this revelation—the standard view of our recent history at many American universities, with just a little tweaking—struck me as both anticlimactic and morally obtuse. Why, then, did it not spoil my enjoyment of Mankell’s book? Was I guilty of a rather unctuous form of self-flattery, congratulating myself for the urbanity and sophistication that allowed me both to enjoy his novel and to judge him as a woefully misleading guide to postwar history?

I plead not guilty. It is true that Mankell’s understanding of the world differs greatly from my own, and not only on political matters. He writes as a thoroughly secularized European, deeply suspicious of faith and especially of Christianity. His novel The Eye of the Leopard (published in Swedish in 1990, a year before he began the Wallander series, though not available in translation in the United States until 2008) makes clear his repugnance for religious conversion. But in Africa—where both Christianity and Islam have long histories—there will soon be more Christians than on any other continent. Mankell would seem to be assuming the right to instruct Africans about how to be authentically African.

Yet there is also much that Mankell and I share, thanks to what the Reformed tradition calls common grace. Most of the time I’m reading him, I’m not conscious of the great gulf between us on certain important matters, and I’m certainly not complimenting myself on my tolerance. Then, as happens in conversation with family members and dear friends, I’m brought up short for a moment: Does he really believe that? Yes, he does. And that experience of difference in the midst of kinship is one of the best reasons to read fiction or poetry in the first place.

There’s another reason for reading Henning Mankell in particular. Elmore Leonard has laid down the law for writers of fiction. According to one of his widely circulated precepts, a novelist should never begin a book by describing the weather. No one reads such stuff, Leonard says. It’s just filler. Henning Mankell (whose sales, his publisher tells us, total more than 30 million worldwide) often begins a novel with a description of the weather (as did Georges Simenon). I like those openings. The only rule to lay down for novelists is this: There are no rules.