Many (oh, yes, many, many) years ago, when I was studying philosophy, certain schools of thought had appealing elements, helped bring coherence to vaguely formed ideas, or opened doors to illumination that I had never imagined. Then it came time to explore existentialism, which I decided, with all the arrogance that an 18-year-old sophomore can bring to the table, was as empty, stupid, corrupt, and sad a concept as the mind of man was capable of creating. Nearly a half-century later, nearly three decades since the death of Jean-Paul Sartre, the most obnoxious of its proponents, I have found no reason to change my mind.

These dire thoughts came to mind as I was reading the new book by Arturo Perez-Reverte, a writer whose novels “The Flanders Panel” and “The Club Dumas” I much admired. But “The Painter of Battles” (Random House, 211 pages, $25) is less a “literary thriller,” as its dust jacket proclaims, than a conversation between two men about the nature of man and morality. Never has the word “thriller” been used with less accuracy; the book moves at a pace slower than bluff erosion. I picked up the book at 7 o’clock, read for more than three hours, then looked at my watch and saw it was 7:30.

Andrés Faulques, a renowned war photographer, has retired to a secluded tower on the coast of Spain. He has exchanged his camera for a paintbrush, deciding to paint a giant fresco on the circular walls of the tower. The painting will incorporate the great depictions of all wars, illustrating in harsh, jagged, cubist brushstrokes man’s inhumanity to man.

Seeking solitude, he is irritated when a visitor shows up. It is Ivo Markovic, the subject of one of Faulques’s most famous photographs, who calmly announces that he has come to kill the artist. This might cause most people to tense up a bit, but Faulques seems mostly curious, and they sit down to talk. Which they do, hour after hour, day after day, ruminating on the painting and old photographs. In a nod to Marcel Proust, many of the reminiscences lead to memories of long-ago events.

The conversation, meant to enlighten, is intelligent-sounding, but it leads always down the bankrupt road of existentialism.

Speaking of war and painting, Andres describes several examples to Ivo, who at one point says he doesn’t understand. “It’s all the same. It doesn’t matter,” Andres answers.

Trying to understand Andres, Ivo says: “Hatred and cruelty should have no place in the world. They’re inadequate. Men destroy one another because the law of their nature, a serene and objective law, demands it. Isn’t that true? In your opinion, intelligent people should kill one another when the time is right, like the executioner who carries out a sentence that means nothing to him … Is that right?” Andres replies, “More or less.”

If I remember Sartre’s “Being and Nothingness” correctly, he espoused the notion that people decide who they will be and, when they realize the futility of their efforts to influence or even to understand the universe, they realize they are alone in a senseless and absurd world. They no longer exist as part of society but are independent, the price for which is loneliness, anguish, and despair.

This is the shore on which Faulques and Marcovic have washed up. The photographer decided to work alone and became famous for the pictures of horrors and depravity he showed to millions around the world. The man who plans to murder him was a victim of one of those wars, having had his wife and son brutally slaughtered. Each has had his soul cauterized, and each has chosen to respond. One decides to kill the man who showed the world his crushed life. The other is already dead, only the muscle, blood, and bone remaining.

Mr. Perez-Reverte is a stylish writer, and he has been most fortunate to have Margaret Sayers Peden perform the much-underrated art of translation. It is possible to turn to almost any page and find a lovely sentence that conjures an image with exceptional clarity and color.

Of one of his photographs, Faulques muses: “It was a good photo. It reflected the chaos of combat in this city, with its slight oscillation at the edges of silhouetted buildings standing amid the explosions and the luminous, parallel straight lines scoring the night sky.”

At the end of the day, however, it all comes to nothing, which was evidently the intent, resulting in a novel less cheerful than Lady Macbeth.

Mr. Penzler is the proprietor of the Mysterious Bookshop and the series editor of the annual “Best American Mystery Stories.” He can be reached at ottopenzler@mysteriousbookshop.com.