It’s a funny question coming from a man who, in the course of 16 acclaimed seafaring novels, has navigated nearly every corner of the globe. But O’Brian’s heart, like his stories, belongs to the 18th century. When he lists his favorite writers–Richardson, Dr. Johnson, Smollett, with Dickens and Proust just making the cut–he speaks of them almost as contemporaries. “Defoe and Cobbett are beautiful writers, although I don’t like either of them as men.” For him the Bronx might as well be on Mars. Still, it has a zoo, and the zoo has hoatzins and a bald eagle, birds that O’Brian, a devoted naturalist, is keen on seeing.

Abandoning the seclusion of his home in the south of France, O’Brian has come to America for the first time in 20 years to promote his new novel, “The Wine-Dark Sea” (261 pages. Norton. $22), the latest installment in the saga of Capt. Jack Aubrey and ship’s surgeon Stephen Maturin. The seafaring adventures set during the Napoleonic Wars have won O’Brian praise from naval historians, cheers from writers including Eudora Welty, Robertson Davies and Iris Murdoch, and downright adulation from a growing cult of readers. Norton has sold more than 600,000 copies of the books, and there is now a Patrick O’Brian newsletter, an O’Brian calendar and a poster. There are also plans to republish O’Brian’s biographies of Picasso and Joseph Banks, the 18th-century explorer and naturalist. Remarkably, all this has happened in the last five years, since O’Brian signed on with Norton, where believers promoted his work assiduously. But at 80, after a lifetime of fiction writing spotted by critical neglect and commercial failure, Patrick O’Brian has seen his ship come in at last. He’s a bona fide literary star.

Given the success he has enjoyed without lifting a promotional finger, you’re left wondering why he bothers now. His itinerary yields the answer. Among the book signings and readings, he has arranged to visit natural-history museums, historical archives and zoos. Norton gets its media events and O’Brian gets a peek at Humboldt’s manuscripts and Audubon’s bird skins.

In person, O’Brian has a Central Casting rightness for his role, his lean, lined face framing a boy’s keen eyes. Brought up in an upper-class Irish family in a time when social form was utterly rigid (naturally lefthanded, he was made to write with his right), he remains impeccably good-mannered. But politeness scabbards steel. His rules for an interview are simple: there will be no questions about his private life.

Otherwise, he’s the soul of loquaciousness, and he speaks as he writes, with a sort of antique limpidity. Asked when he realized that Aubrey and Maturin were ripe material for a long series of books, he replies, “That would have been about the third, or possibly well on into the second book. I saw that if I took them away to sea and kept them in their close community, their wooden world, that I could talk about the things that I wanted to talk about, in a way that suited me, being in a world that I knew intimately, rather than tell other tales of other people in a contemporary background to which I had little to contribute.”

In the years since the first in the series, “Master and Commander,” which never strays far from the conventions of nautical sagas, O’Brian has shed his genre shackles. “The Wine-Dark Sea,” like all the rest, could be the work of only a lifelong sailor, and it has its share of action–an erupting volcano, revolutionary plotting in Peru–but this is a book not about action but about consequences, about what happens to injured sailors after a battle or a battered boat in the storm’s wake. Even Lucky Jack Aubrey has grown reflective, to the bemusement of his more thoughtful friend, who asks, “Do you not think it would be better to go home?”

“Yes, it often occurs to me, but then my innate nobility of character cries out, ‘Hey, Jack Aubrey: you mind your duty, d’ye hear me there?’ Do you know about duty, Stephen?”

“I believe I have heard it well spoken of.”

“Well, it exists.”

Laden with nautical lore and the richly precise descriptions of wildlife that only an avid naturalist could provide, the Aubrey/Maturin books provide a splendid look at a time when irony was merely a condiment to life’s great feast and not the main course it is today. But most important, the books tell the story of a maturing friendship between unlikely friends who hate Bonaparte and love chamber music, and who tolerate their differences with winning and unsentimental generosity. O’Brian is the Homer of an epic of affection.

Departing the zoo, O’Brian feeds giddily on the memory of a flock of scarlet ibises (“Oh dear, those scarlet ibises, oh clear”), and it becomes plain that curiosity about the world is what fuels him so relentlessly (he began the Aubrey/Maturin books when most men are contemplating retirement, and in two decades he has written 16 novels, the Picasso biography and translated the work of Simone de Beauvoir and a biography of de Gaulle). All the way to Manhattan, he asks questions about bridges, trees, birds and the finer points of Texas history. Even when the conversation turns briefly to children, a subject the childless O’Brian might be expected to ignore, the indefatigable naturalist can’t be stopped. “When do they get their teeth?” he wants to know.