Writing is hard. Writing books is harder. So as a mere plebeian author interviewing Dan Brown for the first time, I needed to know: After you’ve sold 200 million books, does it get any easier?

“It’s the same process. It’s identical,” Brown says on a video call from his home library in New Hampshire. “Your characters don’t care how many books you’ve sold; you’re still facing the blank page. What becomes more challenging is you put an enormous amount of pressure on yourself and say, ‘Listen, there’s a certain number of people who trust me.’ If you can get somebody to spend 10 hours with your words, you better deliver.”

It’s safe to say that Brown has repeatedly delivered. A master of the brainy, twisty thriller, Brown’s 2003 novel, “The Da Vinci Code,” is one of the bestselling books of all time, with 85 million copies moved, and was adapted into a box office hit starring Tom Hanks. His novels move with kinetic energy, his plots are intricate puzzles shrouded in religious iconography, ancient cryptography and other obscure arcana. Reading a Brown novel is both a thrill ride and an immersion in real-world facts.

Author T.J. Newman was on a family vacation in Mexico when “The Da Vinci Code” was published. “I didn’t go to the beach. I didn’t go to the pool. I stayed in the hotel room and read,” she told The Times in an email.

“Dan Brown has figured out the nexus point of intrigue and suspense and how to capture the reader and never let them go until the story he is telling ends,” said Newman, the author of bestsellers “Falling,” “Drowning” and “Worst Case Scenario.” “It’s really hard to do that well. And he makes it seem effortless. His instincts about what makes a great thriller are almost unparalleled and you can’t put his books down.”

Brown’s new novel, “The Secret of Secrets,” is perhaps his most ambitious undertaking yet: a dense thriller that is also a meditation on the nature, and the possible future, of human consciousness. The novel kicks off with the theft of a book manuscript from a publishing house — a book, we learn, that may contain the secrets to an entirely new way of looking at the world. The book’s author, Katherine Solomon, is a leading researcher in noetics — the science of parapsychology — and the crux of her thesis is explosive and radical, centering around the concept of nonlocal consciousness, or the notion that our brains are not autonomous machines but rather receptors that acquire consciousness externally.

“It’s no secret that I like to write about big themes,” says Brown. “And there’s no bigger theme than human consciousness. It’s the lens through which we experience reality. I wanted to write about it for a long time and I just hadn’t seen a way in. How do I make something ethereal into a thriller?”

Dan Brown’s new novel, “The Secret of Secrets,” is a thriller that is also a meditation on the nature, and the possible future, of human consciousness.

(Cheryl Senter/ For The Times)

He has accomplished it in typical Brownian fashion: by exploiting consciousness into a potential tool for world domination. For eight years, Brown went deep, schooling himself in cutting-edge brain science and talking to specialists in the field. “I needed to find that pivot point that made it relevant to everyone,” he says. “And I discovered that we have a model of consciousness that’s outdated in the same way the geocentric model of the universe was outdated. This research will change the way we view our world.”

In order to grasp Brown’s story, a quick brain science tutorial is necessary. Normal human consciousness is tied to inhibitory neurotransmitters in the central nervous system called gamma-aminobutyric acid, or GABA. Neuroscientists have now discovered that when GABA levels drop precipitously, our perception of the world can change. That perception isn’t necessarily subjective but is, in fact, a window into another reality that exists beyond our own. Epilepsy patients, who experience dangerous reductions in GABA during seizures, have been known to experience euphoric states in which they receive a sudden flash of what appears to be a reality with which they have otherwise been unfamiliar.

This is similar to anecdotal accounts of humans who have near-death experiences, when the GABA levels drop off entirely, and a new perceptual gateway appears to swing open before them. For years, scientists dismissed these accounts as fantasy, but are now beginning to think otherwise, that the notion of an out-of-body experience, in which our consciousness delinks from our brains and acts as a receiver of another, universal consciousness, isn’t just science fiction. Chris Roe and Michael Daw, two leading noetics researchers, published a widely discussed study last year proposing this very thing. In their paper “Theories of Non-Local Consciousness: A Review and Framework for Building Rigour,” they offer that “consciousness extends beyond the body and the brain and need not be constrained by our usual notions of time and space.”

It is this kind of research that gave Dan Brown his entry point. “I started in a very skeptical place,” he says. “If you asked me eight years ago, ‘Do you believe in out-of-body experiences,’ I’d attribute it to drug hallucinations. Life after death? No way. But my thinking evolved as I burrowed deeper into the science. I know now there is precedent that proves we can have a consciousness outside the body.”

For Katherine, this revelation is the key that will unlock global comity. “Imagine a future in which humans start to lower their brain filters and begin to exist with greater understanding of reality,” she tells her cohort Robert Langdon, the cryptology professor hero of “The Da Vinci Code.” “We might truly start to believe that we’re a unified species.”

But given this is a Dan Brown novel, there is powerful opposition to this idea, and a strong desire to weaponize nonlocal consciousness, especially within the corridors of a certain intelligence agency in Washington. This, according to Brown, is also the stuff of nonfiction. “I have no doubt that the government is involved in this kind of research,” says Brown. “It makes no sense that we wouldn’t. And the Russians are spending a ton of money on it, as are the Chinese.”

“Obviously, there are incredibly difficult moral questions at the root of everything that is being explored in this field,” Dan Brown says of neuroscience. “But I think that, as this new model of consciousness emerges, a lot more good will come of it than evil.”

(Cheryl Senter/ For The Times)

Solomon and Langdon’s search for the book lands them in Prague, a city with a long history of mystical exploration that stretches back to the 15th century. “As soon as I knew I was going to write about consciousness, I knew the book would be set in Prague,” says Brown. “In the days when Emperor Rudolf II ruled, he invited alchemists and Kabbalists to visit Prague and explore the idea of the Great Beyond. The city has long been the locus of this kind of metaphysical thought.” The book also features a golem, which in Czech mythology is a creature fashioned from mud and clay who serves as a moral guardian — a metaphor that Brown uses as “an inanimate creature into which one can infuse life and consciousness.”

Brown is a dogged researcher who grounds his every imaginative fancy in fact. He toured Prague’s famous monuments multiple times, including a huge bomb shelter under Folimanka Park that features in his novel, writing in his notebook along the way. “I try to write down descriptions, rather than take photos, because you may forget certain sounds, such as the way the elevator in Petřín Tower scrapes every few feet during its ascent, or its funky smell,” he says.

Because Brown’s novel is a clash between benevolent actors and those who are bent on exploiting Solomon’s ideas, it’s not hard to draw a parallel to artificial intelligence, a subject that Brown explored in his prior novel, 2017’s “Origin.” Brown is sanguine about AI’s potential; he is not inclined to join the dystopian camp that regards it as an existential threat.

“Humans have never created a technology that has not been weaponized,” he says. “The wheel, fire, the computer. We’ve used them all to kill each other or gain advantage in some way. AI is just another tool and it will be used primarily for good. We’re living in this time when our technological growth is exponential but our philosophical maturity is linear. Computers can fly drones that carry bombs, but 99% of the computers’ usage is affirmative. And I think AI will be the same way.”

For Brown, that optimism extends to the innovations in neuroscience that he explores in “The Secret of Secrets.” “Obviously, there are incredibly difficult moral questions at the root of everything that is being explored in this field,” he says. “But I think that, as this new model of consciousness emerges, a lot more good will come of it than evil.”

Dan Brown at his home in Rye Beach, N.H.

(Cheryl Senter/ For The Times)