By Barry Unsworth

Doubleday. 338 pp $23.95

What a joy it is to have in hand a work of fiction that is at once thoroughly serious and -- as all such fiction should be -- immensely entertaining, in the deepest and best sense of the word. Losing Nelson is original, provocative, stylish and intelligent, the most accomplished and interesting new novel I have read since John Derbyshire's Seeing Calvin Coolidge in a Dream.

To call it a novel is to do it incomplete justice, for it is also what William Styron called The Confessions of Nat Turner: "less an `historical novel' in conventional terms than a meditation on history." Just as Styron considered slavery and its legacy through the story of Nat Turner, leader of the most famous American slave rebellion, so Barry Unsworth contemplates heroism and its true character through the story of Horatio Nelson, the greatest of all English heroes.

The book arrives at an auspicious moment. On both sides of the Atlantic, books about the sea and those who sail it are much in vogue. This seems to have been set off by the surprising and much deserved popularity of Sebastian Junger's The Perfect Storm, not to mention the Aubrey/Maturin novels of Patrick O'Brian; but whatever the explanation, we are now awash in nautical literature, a surprising amount of which is very good indeed. If this fad leads more readers to Losing Nelson than might otherwise be drawn to it, they will find themselves rewarded with the best book of the lot.

But though Nelson was a magnificently accomplished seaman, this is at heart a book not about the sea but about a man and, even more than that, a legend and a myth. Two men, to be more accurate, for Losing Nelson has two protagonists: Nelson himself, of course, and the narrator, a 42-year-old Englishman named Charles Cleasby, "two faces side by side, two lives in parallel." Since the age of 13, "during a history lesson, when I discovered that Horatio Nelson lost his mother when he was nine years old," just as Charles himself did, he has been convinced that "nothing that ever happened to Horatio did not also happen to me," that he is somehow the darker half of this bright and shining hero. Recalling a decisive moment in Nelson's career, when he went against orders and boldly took his ship off on its own, breaking the British line of attack against Spain, Charles writes:

"At the moment that he swung away from the wind and broke the line, risking the outcome of the battle and his whole career on this one throw, at that moment, in his 39th year, Horatio became an angel. He entered a different sphere. I will say what I think angels are. They can be dark or bright, but they all have the gift of spontaneity, of creating themselves anew. This is a pure form of energy, and Horatio was winged with it. All the same, angels are not complete, they need their counterparts, the dark needs the bright, the hidden needs the open, and vice versa. Sometimes they meet and recognize each other."

Believing himself to be Nelson's dark alter ego, Charles devotes his days and nights to ceaseless hero-worship. He seldom leaves his house, staying down in the basement with the pool table that he has converted into a miniature seascape and covered with model ships. With these he re-enacts, on the exact days and hours they actually occurred, the great battles of Nelson's life, always coming to the climatic moment on Oct. 21, 1805, when the British fleet under his command met the combined French and Spanish navies at Trafalgar. "England expects that every man will do his duty," he so famously exhorted his men, and led them into the battle in which France and Spain were routed and Nelson lost his life, becoming an instant immortal.

Not merely does Charles re-enact Nelson's battles, he is writing a book, "the best account of Horatio ever to appear in print, a profound study of the man and a lasting tribute to the hero." It is a hagiography, but the deeper Charles gets into it the more he is vexed by the inconvenient truth that in Naples in June 1799 Nelson committed what Robert Southey, his first important biographer, called "a stain upon the memory of Nelson and the honour of England." The tale is complicated, but in essence it is that he turned over the imprisoned leaders of the Jacobin uprising in Naples to the city's royalists, who murdered them at the gallows, one by one, more than a hundred in all. Charles simply refuses to believe what history tells him:

"Horatio could never have stooped to such a thing. His nature was too noble; he was the incarnation of the spirit of fair play, that profoundly British virtue, for which we are known far and wide. But the slanders had persisted, maintained an evil life on their own, in spite of his many champions. Buried somewhere in this great heap of argument, two centuries old by now, was the bright fragment that would clear his name. How glorious to be the one to find it, to see it glint like gold among the husks of old polemic. My name would be joined with his for as long as his deeds were remembered. Charles Cleasby, the vindicator of Horatio Nelson."

To assist him in his labors Charles engages the services of Avon Secretarial Services's Lillian Butler, "a steady person, in her early thirties," whom he calls -- in his mind, not to her face -- Miss Lily. She is quiet, literal-minded, inquisitive, insistent, somewhat oblique. At first she simply takes down Charles's words, but her curiosity is piqued. She begins to read up on Nelson on her own and, worse, she begins to ask questions and to form opinions. She refuses to accept Charles's judgment that Nelson was a demigod and insists on seeing him as a flawed human being, one who had been shipped off to sea at the age of 12 as a midshipman, which she sees as "a way of processing people," and "as far as I can see they've been processing him ever since." She continues:

"Why couldn't they say, Well, yes, he was a great admiral and a very brave man, and yes, he was generous and warm-hearted, and he won a sweeping victory at the hour of his country's need, but he was narrow-minded and eaten up with vanity and could never admit he was in the wrong? He was a person, in other words. But no, they had to make him into a great man. . . . I can't help it, he puts my back up -- Nelson, that is. He was always so ready to get people killed. If you look at it one way, he was a sort of serial killer. I like men who are gentle and kind and try not to hurt anyone. Women too, for that matter."

Charles is infuriated by Miss Lily's words: "All these years of celebrating the Battle of the Nile and now I had to listen to questions from Avon Secretarial Services, try to understand the way this woman associated things together. She had soured his great victory with this talk about pity." But then Charles looks closely at a portrait of Nelson and sees "a different, crueller face," a man who "looked like a god glutted with sacrifice." For all those years he had seen only "death or glory, the genuine heroic impulse"; now he must confront "all those men, all the blood and rending of the flesh."

Questioned and challenged and vexed by Miss Lily, unable to find the "bright fragment" that would clear his hero's name, Charles at last forces himself into action. He goes to Naples to see the scene for himself, convinced that the answer is there. He makes a date with a man named Sims, author of minor studies of Nelson that he had found congenial, but Sims does not deliver as expected. Nelson was no hero, he tells Charles. The real heroes were "the Neapolitan Jacobins who went to the scaffold in the name of liberty in 1799, sent there through the good offices of Lord Nelson." Ferdinand, king of Naples, in his thirst for vengeance "strangled or decapitated or shut away the whole of the Neapolitan intellectual class."

It will be argued, no doubt, that in drawing these conclusions about Nelson, Unsworth is applying the convictions of the 1990s to a man of the 1790s. There is some truth to this. Nelson was of his own times, not of ours, and deserves to be judged accordingly. But Unsworth's most penetrating judgment is not directed against Nelson -- whose heroism was real, as even Miss Lily acknowledges, "but who was a human for all of that" -- but against us, the people in the crowd who yearn for heroes and manufacture them in what Sims calls "the national dream factory." Charles, who dreams so passionately and so wrongheadedly, becomes a kind of Everyman, and when he finds disillusionment in Naples its meaning transcends him:

"The same questions. I was no nearer the answers here than I had been in my basement. . . . Standing there with that dull band of pain along my brows, I felt the same sorrow, the same helplessness that I had so often felt at home in my study. Whatever one made of the documents, the truth of the past was beyond grasping -- it lay in the looks exchanged, the tones used, and the eyes and voices had left no trace."

Poor Charles; he has many losses, all hard. But at the end of this fine book -- a book that echoes in the mind long after it has been read -- it is hard indeed to draw the line between "poor Charles" and "poor us."

Jonathan Yardley's e-mail address is yardley@twp.com.