Author Carlos Ruiz Zafon photographed at the Former residence of the Spanish ambassador in Washington, D.C. (Marvin Joseph/The Washington Post)

Carlos Ruiz Zafón owns side-by-side apartments in Beverly Hills.

One is home. The other he calls his “Dragon’s Cave.”

In the Dragon’s Cave, the international mega-bestselling author of “Shadow of the Wind” has scattered more than 400 statues and other representations of dragons — the year of his birth on the Chinese calendar. But the most important object is a grand piano.

When he’s stuck on a character, struggling to fit his invention into his complicated, intricately constructed narratives, he will reach for the piano keys. There, in the act of composing, he finds that he can unlock secrets about his characters that had eluded him.

By the time he finishes writing each book, the self-taught musician has composed something akin to a film score. But Ruiz Zafón — generally thought to be the most read Spanish author since Cervantes — doesn’t want to see his books adapted for the big screen.

He has engineered them so precariously, built such labyrinthine, interlocking plots, that he fears the stories would pop like tension-loaded springs if someone tinkered with them.

“To adapt it would be a betrayal of the work,” he says. “If you touch it, it will explode. Nobody can make it better because nobody knows how it was put together. A lot of devices, they’re pushed to the limit. It’ll explode.”

So adamant is he about this, that he has considered putting language in his will to assure his books are never, never, never made into films — even after his death. This insistence makes Ruiz Zafón an outlier in the world of blockbuster authors, and it might explain, in part, why he is the literary sensation so many people have never heard of, or at least might struggle to name.

“There’s nothing noble here,” he says. “I have the luxury to say, ‘Thank you very much. But no thank you.’ ”

“Shadow of the Wind,” the first of a four-novel cycle called “The Cemetery of Forgotten Books,” has sold more than 18 million copies worldwide, according to his agent, a figure that places him among the most read living literary authors. He has sold more than 35 million copies total, and been published in more than 40 countries — not just throughout the Spanish-speaking world, Europe and the United States, but also in Brazil, Lithuania, South Korea, China and India.

Carlos Ruiz Zafon talks with an audience about his books and his creative process at the Former residence of the Spanish ambassador. (Marvin Joseph/The Washington Post)

The final book in the cycle — “The Labyrinth of Spirits,” which will be published next month in Europe, but not until 2018 in an English translation — will tie up diverging plotlines and clarify the story of the mysterious author, Julian Carax, who figures prominently in “Shadow of the Wind.” It will also feature a new face, a woman named Alicia, who Ruiz Zafón says is one of three characters intended to represent parts of his own personality.

His books, set in Barcelona, have spawned a bustling industry of walking tours that thread through the city’s narrow, sinuous streets tracking his characters’ movements. But he has written all the novels in Los Angeles, while still maintaining a home in his native Barcelona.

“I used to joke I have a DVD memory,” he says. “Perspective. Light. All these things I memorize. Barcelona is something I’ve been absorbing all my life. I don’t need a map.”

Ruiz Zafón is a tall, thickly built man, who favors chunky, round glasses. He would rather meet a couple of friends for a quiet dinner than go to a party. He is not into making the scene. Small talk bores him.

When he came to D.C. for a recent book event, he celebrated his 52nd birthday by going to bed early at his hotel. He does not have an espiritu verbenera — a partying spirit.

“I don’t talk much,” he says with a shrug moments after sitting down one afternoon for a late lunch in downtown Washington, the day after appearing at the National Book Festival.

His throat was sore, which happens every time he goes on tour. His vocal cords are delicate instruments for lack of use, he says. He sought relief from one of those fancy Los Angeles doctors who minister to pop singers. But it was still scratchy.

Changing cities and careers

As a young man in Spain, Ruiz Zafón — whose grandparents were illiterate factory workers and whose father was an insurance agent — went into advertising.

“I became kind of a hot creative person, whatever that is. Even though I was making a fortune — money that only people in organized crime or rock and roll are going to make — I hated it. I hated myself for doing it.”

He quit to write full time. His first book, “Prince of Mist,” a young adult novel, was a hit and won a major literary prize.

Success, just as it had in advertising, didn’t particularly make him content. A Spanish friend had moved to Los Angeles to write screenplays. Ruiz Zafón thought he would too.

In Los Angeles, he found a city that felt a world apart from his hometown. Barcelona was ancient. Los Angeles seemed fresh and new.

Screenwriting, though, didn’t work out as he’d imagined. He would “always end up saying the wrong things at meetings,” he recalls. “Sooner or later they’ll see it in my eyes — that moment I think that this is really stupid.”

He worked on projects that would never get made. He feared slipping into the “netherland of lost souls of L.A. It does not have nine levels to it. It’s got like 9,000 — with sub-divisions.”

But he was still writing novels from an apartment with a view of the Hollywood sign.

“I didn’t join the legion of lost souls because I still had my little books,” he says. “These were real.”

Author Carlos Ruiz Zafon. (Marvin Joseph/The Washington Post)

By the mid-1990s, he’d written four young adult novels that were doing reasonably well in Europe, but none of them were exactly what he aspired to create. He called his young-adult publisher and declared: “I’ll never give you another book again.”

He had set his books in places such as southern England, Kolkata and Normandy. When he made his pivot to adult literary fiction, he turned his mind toward home.

“I didn’t want to use Barcelona as a backdrop,” he says. “I wanted it to be a character in the book.”

And so when Daniel Sempere, the young man at the center of “Shadow of the Wind,” is introduced to readers, he is propelled into a place of mystery by a city that seems to tug him along.

“The lamps along the Ramblas sketched an avenue of vapor that faded as the city began to awake,” Ruiz Zafón writes in the opening to “Shadow of the Wind.” “When we reached Calle Arco de Teatro, we continued through its arch toward the Raval quarter entering a vault of blue haze.”

“Shadow of the Wind” was published in 2001. It sold well, but also lingered, its sales growing exponentially by word of mouth.

A European publisher recommended the book to a New York-based editor and agent, Thomas Colchie, who happened to have a lunch scheduled with Scott Moyers, the publisher of Penguin Press. Moyers was not only planning a trip to Barcelona at the time, but he’d also been thinking he’d love “to publish the great Barcelona novel.”

Colchie just happened to have one for him.

“Shadow of the Wind” was published in English in the United States in 2004, lushly translated by Lucia Graves, an author who is the daughter of famed English poet Robert Graves. It got a boost in 2007 when novelist Stephen King raved about the book in Entertainment Weekly.

“If you thought the true gothic novel died with the 19th Century, this will change your mind,” King wrote. “Shadow is the real deal, a novel full of cheesy splendor and creaking trapdoors, a novel where even the subplots have subplots.”

When Ruiz Zafón reads a book, he can’t help “reverse engineering,” he says. Lately, he has been consuming noirish detective novels, particularly those of Michael Connelly, Dennis Lehane and George Pelecanos.

Once Ruiz Zafón is finished writing a book, he doesn’t want even a comma changed.

“I write it and rewrite it and rewrite it a million times. Then I do it again. Then I re-edit,” he says. “I’m extremely hard to edit. Almost impossible to edit. Because I’ve already done that.”

His sleeve slides back when he reaches for a cup of tea, revealing a burly Breitling Unitime with a dial that provides the current time in locales as far flung as Kiev and Tonga. Ruiz Zafón loves watches, marvels at their precision and complexity. The clear underside of this model lets him observe the inner workings in detail.

When he talks about his own work, he often returns to images of mechanical wonder. He extends his fingers, interlocking them like the toothed wheels of a gear.

He is disdainful of authors who attribute literary accomplishment to miraculous inspiration, “as if the muses were whispering in your ear.”

Ruiz Zafón prefers to think of writing like a craftsman might think of building a watch.

“It’s like engineering in a way,” he says, deep into a layered meditation on craft, oblivious to his scratchy throat. “It’s made of a million tiny pieces.”

The man who loves watches hasn’t looked at his in a while. The man who doesn’t talk much has been talking for four hours. He wants to go for a walk now. On the way, he says. “we can talk some more.”