In “The Ghost,” Robert Harris’s previous best-selling novel, America’s tetchy relationship with the rest of the world is explored indirectly, from the perspective of a British writer who comes to believe that an ex-prime minister is in the pocket of the CIA. In “The Fear Index” — released in the United States last week — the subject matter is again close to home, but 5,000 miles away.

This time, the main character is an American living in Geneva, witnessing (causing?) a financial collapse that results in worldwide panic.

“It seemed to me that the dominant characteristic of this character would be a kind of nerdiness,” Harris explains. “A kind of cut-offed­ness from the world and from humanity, and so . . . ”

And so you decided to make him American?

“No! And therefore it didn’t matter what nationality he was. . . . He belongs to the international community of the geek.”

Harris, 55, belongs to the international community of the airport reader — the people of the paperback who demand burning plots and tense suspense. His stuff is Dan Brown, but better written. It’s Ken Follett, but less discovered. He does refined thrillers; he does restrained mania; he does social commentary disguised as potboiler. The global press has mostly glowed over “The Fear Index,” and a movie is in the works. Harris will write the screenplay, as he did for Roman Polanski’s adaptation of “The Ghost.”

Now, Harris is visiting Washington from his home in England, nibbling a steak at Kramerbooks’ Afterwords Cafe. The location has been cheekily chosen because of its dead-tree symbolism, which is at odds with the setting of “The Fear Index”: a hedge fund whose employees are chastised for carrying paper.

Alexander Hoffman is the American physicist who runs this fund, having populated it with the brainiacs he poached from a previous stint at Cern’s massive particle accelerator. Other characters include his artist wife, his vaguely sweaty business partner and the mysterious bald man who breaks into Hoffman’s chateau in the middle of the night and tries to kill him.

And the machine. The machine is the VIXAL-4. It is Hoffman’s pet project and cash cow, designed to predict market behavior based on its understanding of human fear. It might be responsible for everything that goes wrong in the novel. Or it might not. Everything might be in Hoffman’s head.

The resulting book comes off as a mash-up between “The Turn of the Screw” and “2001: A Space Odyssey,” although Harris had a more classic inspiration:

“I really think of it more as modern gothic,” he says.

Think Du Maurier — both George and Daphne. Think Mary Shelley. The Geneva setting of “Fear Index” is a homage to “Frankenstein.” Shelley was famously vacationing in Switzerland when she conceived of a scientist being betrayed by his own hideous invention.

There is plenty of room for monsters in the modern world, Harris says. The 21st-century gothic novel would not involve reanimated corpses, however, but anthrophomorphized technology.

Even the way we describe market collapses, he says. “We say ‘the market plummets,’ like it’s some roaring creature,” as though it has its own agency and self-interest.

Whether a novel is about Frankenstein’s monster or about Hoffman’s VIXAL-4, “it’s all about the hinterland between human and other — the idea of something encroaching on the very center of our existence, the . . . ”

And here, Harris cuts off.

Not him, personally, but the recorder on which this interview was captured, which mysteriously decided to fizzle out halfway through an hour-long conversation.

The monster is in the machine!

Harris is a former BBC journalist whose first foray into writing a novel, “Fatherland,” explored a what-if-Hitler-had-won alternative history of Germany, and made him a household name in Britain. He followed that up with “Enigma,” about World War II code-breaking, and he is two-thirds of the way through a historical trilogy about ancient Rome.

Pompeii,” the first in the series, is a fictionalized account of the eruption of Mount Vesuvius. It’s been praised for capturing the giddy excess of a bustling civilization that didn’t realize it was on the verge of collapse. In some ways, this is what many of his works have been about: The charismatic prime minister, about to fall. The delayed but inevitable implosion of Nazi-run Germany.

When Harris first conceived of “The Fear Index” in the late 1990s, the business world was abuzz with the concept of digital companies — the types — existing in the real world. By the time he finally plotted the book, he was more interested in how a real company would function in a culture that has become relentlessly digitized, a culture in which our online selves threaten to overshadow our real-world existence.

In other words, “The Fear Index” is also about a civilization on the verge, and the panic from reading it is less about what will happen to Alexander Hoffman than what will happen to us all.