Somewhere on the global oceans of the imagination, "Lucky Jack" Aubrey is sailing against Napoleon.

He may be along the French coast where he's prone to the ship-stealing harbor raids known as "cutting out expeditions," or in the Salibabu passage near the Sulu Sea where he chased the man-of-war Cornelie after being shipwrecked in a typhoon en route to Batavia. Or on the Ionian shore where he out-fought the treacherous Mustapha Bey, or even off Barcelona where his masterly ship-handling defeated the dreaded and incomparably named 32-gun Spanish xebec Cacafuego.

But one thing's for certain. With him will be his brilliant, wheyfaced alter ego Stephen Maturin, the half-Irish, half-Catalan surgeon-spy and sometime opium eater, whose passion for natural science forever leads him on misadventures in search of the thick-kneed curlew or some such ornithological triumph, and who in Australia nearly lost his life to the little-known poisonous spur of the duckbilled platypus.

Only one person knows what Aubrey and Maturin are currently up to: a polymathic septuagenarian named Patrick O'Brian, who lives in Arcadian retreat in the South of France and almost never gives interviews. In the past 22 years, in between writing the definitive biography of Picasso and translating the works of Simone de Beauvoir, he has written 15 Aubrey-Maturin novels. To his growing cult of readers, the difficulty finding these treasures in bookstores has ranked among the great crimes of the century.

Last year, on the front page of the New York Times Book Review in an article called "An Author I'd Walk the Plank For," Richard Snow, editor of American Heritage Magazine, called the Aubrey-Maturin books quite simply "the best historical novels ever written."

"There is not a writer alive whose work I value over his ...," wrote Stephen Becker this year in the Chicago Sun-Times. "It accomplishes nobly the three grand purposes of art: to entertain, to edify and to awe."

Other writers and critics on both sides of the Atlantic, from Eudora Welty and Philip Caputo to Robertson Davies and Iris Murdoch, have been similarly enthused. In London, the Times Literary Supplement pronounced the books "a brilliant achievement." Said the Irish Times: "No writer alive can move one as O'Brian can ... can make you laugh so loud ... whiten your knuckles with unbearable tension or choke with emotion. He is the master."

If those claims seem extravagant for books that might sound at first like nautical bodice-rippers, it may be because historical fiction, like history itself, has been so debased in our time. Who today crafts compelling period page-turners with the art and intelligence of Kenneth Roberts ("Northwest Passage," "Lydia Bailey") or C.S. Forester ("Captain Horatio Hornblower") or Nordoff and Hall ("Mutiny on the Bounty"), most of whom toiled nearly half a century ago?

Almost the only possible answer is O'Brian. Yet to compare even the best of his predecessors to him is to compare good straightforward table wine with the complexity and elegance of great Bordeaux.

While his stories are thumping great adventures, replete with suspenseful sea chases, swashbuckling battles, shore-side intrigues and the global scope of empire, his characters don't just navigate the earliest years of the last century; they talk, eat, breathe and exude them, immersing the reader in the process in all the civility and cruelty, elegance and filth, erudition and ignorance of their age.

Whether he's watching Aubrey order hawsers aloft to reinforce his topmasts against a threatening press of sail, or describing Maturin opening the skull of a head-wounded seaman (and closing it with a flattened three-shilling coin), or narrating their joint ruminations on the political leanings of the sultan of Palo Prubang, O'Brian's detail work is at once staggering and irresistible.

Where else can you discover that young officers in the age of Nelson competed in extravagant poetic compositions ("But he who strives the tempest to disarm/ Will never first embrail the lee yardarm")? Or learn the nocturnal habits of the Batavian fruit bat? Or encounter such ship-borne culinary delicacies as mutton bird fritters, soused hog's face and a much-prized species of pudding known as "drowned baby"?

Aubrey and Maturin themselves are both archetypal and unique: Aubrey hefty, convivial and handsome, part Tom Jones, part John Paul Jones; Maturin, small, sallow and untidy, that contradiction in terms, an intellectual Sancho Panza. The author of such admired works as "Diseases of Seamen" and "Tar-Water Reconsidered," Maturin is the sort of enthusiastic, woolly-headed scientific prone to dissecting orphan cadavers in the garden shed or carrying a bottled Arabian dormouse in his pistol holster.

The improbable friends share an unquenchable love of music and -- Aubrey on violin, Maturin on cello -- are wont to while away the odd equatorial evening sawing away together in the after-cabin at Mozart or Boccherini.

If Maturin, with his weedy enthusiasms, rumpled meditations and cryptographic skulking (he gathers intelligence for the admiralty), is an obvious novelist's delight, O'Brian is clearly just as interested in the less obvious complexity of Aubrey, whose crack-on-the-sail heartiness masks an inner emotionalism that both confuses him and gives him peace:

He was eating his dinner not in the dining-room but right aft, sitting with his face to the great stern-window, so that on the far side of the glass and a biscuit-toss below, the frigate's wake streamed away and away from him, dead white in the troubled green, so white that the gulls, poising and swooping over it, looked quite dingy. This was a sight that never failed to move him: the noble curve of shining panes, wholly unlike any landborne window, and then the sea in some one of its infinity of aspects; and the whole in silence, entirely to himself. If he spent the rest of his life on half-pay in a debtors prison he would still have had this, he reflected ... and it was something over and above any reward he could possibly have contracted for.

O'Brian, however, is more than a skilled tale-teller, researcher and stylist. Most artful of all is his capacity to fashion from the everyday concerns of his characters, and even from their smallest small talk, a moral mirror for our own age.

When Aubrey and Maturin arrive on the Turkish coast to probe the possibility of alliance with a local sultan named Ismail bey, they are met with apologies for the bey's tardiness in asking them to dine: He "had been hunting in the marshes and news of the frigate's arrival had not reached him ... "

" 'What was the Bey hunting?' asked Jack, who was interested in these things ...

" 'Jews,' said Graham, relaying the question and the answer.

" 'Pray ask the Effendi whether the pelicans nest here,' said Stephen, after the slightest pause. 'I am aware that the Turks have a great kindness for the stork, and never molest her; perhaps their humanity may extend to the pelican ...' "

Crossing the Atlantic

For those who've stumbled recently into the swelling cult of O'Brian enthusiasts, the most astonishing aspect of his work is that it was all but unobtainable in this country until four years ago.

While the first five Aubrey-Maturin novels -- "Master and Commander," "Post Captain," "H.M.S. Surprise," "The Mauritius Command" and "Desolation Island" -- were published in England between 1970 and 1978 by William Collins Sons & Co. Ltd., no one seemed to know what to do with them on this side of the Atlantic. They attracted few American readers.

"I think the rather patronizing judgment was that there was somehow no constituency in the States for this sort of 'high novel,' " says Richard Halstead of W.W. Norton, O'Brian's publisher here since 1988. "But one of our editors, Starling Lawrence, is an absolute fanatic about O'Brian and lobbied passionately for us to acquire his rights over here. Once we did, the decision was to bring over what was then the latest book {"The Letter of Marque"} and see how it did. It did well, and we have been bringing out the rest of them a few at a time ever since." The most recent Aubrey-Maturin volume, "The Truelove," was published here in April.

Snow's article in the New York Times last year gave the books a major boost, Halstead said, and since then they've been selling "extremely well."

"I mean, he's not Danielle Steel" in terms of sales, "but we're extremely pleased. He's been selling at a brisk and constant clip -- about 1,000 copies a month for each of the 15 titles."

More significant than O'Brian's numbers, however, Halstead says, is the passion of his U.S. fans. "They phone us. They write long letters of gratitude for the books. They besiege us with inquiries about when the next one is on the way" -- so many inquiries that Norton has started a Patrick O'Brian newsletter to stanch the flow.

Those readers, a disproportional number of whom are women, tend to be "somewhat older than the average book purchaser and extremely well read," Halstead says. "They tend to be located more on the East and West Coasts than in the central part of the country, and they order frequently from book clubs and catalogues. And, of course, they are very curious about O'Brian."

That curiosity is unlikely to be soon satisfied. The author is an intensely private person, Halstead says, with no apparent attraction to media celebrity. What clues we have to his life and personality must be gleaned from a few literary sketches of him over the past few years, mostly in British papers, and the sporadic but always intriguing author's notes with which he introduces his volumes.

An apparent Irish native, he has lived since 1949 near the town of Perpignan in the foothills of the Pyrenees above the Mediterranean. There he pens his novels longhand, 1,000 words a day, in a rocky tunnel adjacent to the wine cellar that holds, among other sleeping treasures, the fruit of his own vineyard.

Having read classics and philosophy in Britain and France in the '20s and '30s and lived briefly in Wales after World War II, he settled down to full-time writing in France with his wife, Mary, to whom almost all of the Aubrey-Maturin books are dedicated, sometimes in Latin or Greek.

In addition to the Aubrey-Maturin books and the Picasso biography, he has published five other novels, four volumes of short stories and a biography of the famous 18th-century naturalist and discoverer Joseph Banks, plus numerous translations from the French, including the popular novel "Papillon." How, in all that time, he has escaped greater fame, as British critic Peter Wishart has written, "is one of the literary wonders of the age ... as baffling as the Inca inability to invent the wheel."

There are some obvious partial answers. The Aubrey-Maturin books, for all their sprawling geography, are maddeningly deficient in maps, particularly when Aubrey is executing some intricate rendezvous or expedition.

O'Brian is scarcely more helpful in guiding the reader through the rocky shoals of early 19th-century language, whether nautical, scientific or merely idiomatic. Arcane terms like "futtock" and "cathead," "orlop" and "poldavy" bombard the reader at times with the weight of names in a Russian novel, confounding even the most dedicated antiquarian or sailor. Even Maturin -- an incurable landlubber -- grows impatient with them at times and protests.

Furthermore, as precise as he can be about the set of every sail and the Latin names of insects or shrubs, the author can sometimes be frustratingly oblique in his narration. Does Aubrey, for example, ever actually bed Maturin's great and only partially requited love, the magnificently liberated Diana Villiers? We never really learn.

There is also the reclusiveness of the author himself, who Halstead says has repeatedly resisted efforts to lure him into the spotlight. "He won't answer questions about his personal life," Halstead warns, "and who can blame him? He's a very civilized gentleman, 78 years old, and he believes, as Maturin says in one of the books, that 'question and answer is really no civilized form of conversation.' "

"That's eminently true," says O'Brian, his eminently cultivated voice finally reached, after some negotiation, via telephone at his home in the South of France. But, while adroitly -- and with great courtesy -- sidestepping anything approaching direct cross-examination, he conditionally permits a peek or two at the author's life.

It is tea time there, after his morning's writing and after a lunch that typically runs to various pates, many sorts of cheeses, and after an afternoon of puttering around his vineyard -- a vineyard visited regularly by wild boar. A nearby lagoon holds wild flamingos.

"As I sit now I look out on a Pyrenean mountainside with a Charles V castle on top it it. And an orange tree in our cloister between me and the castle." If one is going to live for years on a writer's meager pay, he suggests, "it is perhaps an improvement over the ordinary view from a London garret."

O'Brian says he never set out to write a series of books set in the age of sail. He had shipped out on square-rigged ships as an adventurous youth "on long vacations and that sort of thing." But it's not as if his career began with Jack Aubrey.

In 1952, Delmore Schwartz in the Partisan Review critiqued O'Brian's first novel, "Testimonies" (set in contemporary Wales and scheduled for republication by Norton next year) alongside John Steinbeck's "East of Eden," Evelyn Waugh's "Men at Arms" and Ernest Hemingway's "The Old Man and The Sea." He found it by far the best of the lot.

Citing the book's "lyric eloquence" and "enchantment of story," he wrote: "In O'Brian, as in Yeats, the most studied literary cultivation and knowledge bring into being works which read as if they were prior to literature and conscious literary technique."

Why does a writer with notices like that desert his own century for the watery world of the past?

Well, O'Brian says, why not?

"It never occurred to me, that to shift the scene of a novel to another age ... and to cast it in an English in some degrees more pleasant than the current, put me in a disreputable genre."

He began his literary voyage into the past in 1970, just as an entire generation was announcing -- far too loudly and far too soon -- that the past no longer had any relevance to the present. But times, like tides, have a way of changing. What does he think about his recent rediscovery by critics and readers, nearly half a century into his career?

"It's agreeable," he says. "But I wasn't overwhelmed with woe when it didn't happen ... People are often out of phase with their generation."

Besides, he says, he was too wrapped up in Aubrey and Maturin, who now seem like perpetual guests in his home. He never tires of them, and is now well into the book he knows only as "Number 16," handing each chapter to his wife for critical comment as he finishes it.

"She's been very kind about it. But I have various doubts, you know, and I put them to her and in those cases she always answers truthfully. And that may be painful. She says 'This won't do' and out it goes."

Much of his historical framework, as well as its detail, he says, he lifts from the records, letters, diaries and other contemporary accounts of the Royal Navy of the 18th and early 19th century where "so very often the improbable reality outruns fiction."

Ebbs and Flows

He shows no sign of exhausting his imagination. Though each book is essentially self-contained, the Aubrey-Maturin series is better thought of as a single multi-volume novel, that, far beyond any episodic chronicle, ebbs and flows with the timeless tide of character and the human heart. Not every book hinges on a great battle, for O'Brian is far more fascinated with people and their interactions than with gunnery. Often he's content simply to submerge his reader in the microcosm and metaphor of shipboard life, implicitly asking us to consider how and why such a brutal and confining society (unlike ours?) could nourish such triumphant humanity.

"I remember Bourville's definition of a novel as a work in which life flows in abundance," says one of Maturin's friends, "swirling without a pause or, you might say, without an end."

Three years ago, in describing for the Times of London how he spends his day, O'Brian said when he retires at night he is usually "listening to some tricky contrapuntal music" akin, perhaps, to those Aubrey-Maturin string duets in the after-cabin. "One part of my mind follows it closely," he said, "while another part carries on with the book I am writing. That's when the dialogue takes fire -- and I laugh, or cry 'God damn your eyes!' " And in a flush of inspiration he retreats to the next room, to steer Aubrey and Maturin onto a new tack in their -- and our -- enduring voyage of discovery.