"Collecting," muses Susan Sontag in her latest novel, "is a succession of desires…. To collect is to rescue things, valuable things, from neglect, from oblivion, or simply from the ignoble destiny of being in someone else's collection rather than one's own."

In The Volcano Lover, Sontag has rescued a story locked in many a biographer's prized collection: the tangled fortunes of Lady Hamilton and Lord Nelson, whose notorious liaison scandalized eighteenth-century Naples. In a sense, though, Sontag's observations about collecting apply more slyly to herself as a writer. In her revisionist retelling of the Hamilton sage, she's found the ideal forum to display her own succession of desires. For The Volcano Lover is no less than a Grand Tour of ideas that have animated Sontag's fiction and nonfiction these past three decades: the primacy of aesthetics, the totalitarian impulse to sacrifice intellectuals, the moral role of art in history. Sontag's passion for ideas channels itself into the arenas of passion—political, amorous, aesthetic—all played out on a vast cultural stage, the ill-fated republican struggle for Naples.

A historical romance by Susan Sontag? Is this the ultimate literary oxymoron? A tempting parody by our premier intellectual voice, whose essays on Canetti, Barthes, Benjamin and Bresson are classics in avant-garde criticism? Surely if two words define Sontag, they are "Against Interpretation," not "A Romance," the subtitle of her new novel. If we know anything about the author of On Photography and Illness as Metaphor, it is Sontag's capacity to surprise, to challenge our received opinions. With The Volcano Lover, it is the writer herself who has most skillfully resisted interpretation.

Sontag's foray into historical romance parallels that of another sophisticated theorist, A.S. Byatt, whose 1990 Booker Prize-winning novel Possession rocketed her to best-sellerdom. Fittingly, Byatt's literary scholar protagonists are entangled in the area often associated with Sontag: the thicket of critical theory. Sontag's quarry, as Elizabeth Hardwick has noted, is "the wide, elusive, variegated sensibility of modernism." If, most recently, she's explored it with elegiac precision in AIDS and Its Metaphors (1989) and its fictional counterpart, The Way We Live Now (1991), her most successful statement is the novel at hand. The Volcano Lover is a literary conceit: an eighteenth-century story within which Sontag illuminates the inexorable pull of the past on modern life.

The germ for the novel has long resided in one of her strongest stories, "Unguided Tour." Collected in I, etcetera (1978) (and also the subject of her fourth film), it's a spare conversational duet between lovers wandering the ruins of Italy and their own relationship. Travel as consumption: objects, scenery, monuments. Travel as repetition: language, memory, history. Taking her cue from one of the lovers, Sontag sets herself a dare as an author: "Say to yourself fifty times a day: I am not a connoisseur, I am not a romantic wanderer, I am not a pilgrim." That single line gives The Volcano Lover its theme and its literary license.

Style, as Sontag notes in "Against Interpretation," "is the principle of decision in a work of art, the signature of the artist's will." How remarkable and radical a departure this new fiction is from those willfully opaque puzzle novels The Benefactor (1963) and Death Kit (1967). In The Volcano Lover, Sontag finally achieves the "transparence" she cites as the hallmark of all true art. Gone are the artful elisions of Barthes. In their place are the thunder and props of narrative, the very narrative she's banished in previous fiction. And how skilled a story-teller she is. Like Byatt, who ingeniously mimics the moral spaciousness of the nineteenth-century novel to reflect on our own century, so Sontag has found her ideal counterpart in the eighteenth century's elegantly aphoristic novel of ideas.

What more fitting setting than Naples, "capital of natural disaster," to serve as the backdrop for "the telluric forces" of the late eighteenth century? Rocked by revolutionary upheaval, it is the age of royalists and republicans; art and artifice; romanticism and rationalism. An age that crackles with change: Franklin's experiments with electricity; Marat's incendiary Jacobinism; Europe's gleam of the guillotine blade. Yet it's Vesuvius, volcano as entertainment and apocalypse, that provides Sontag with the ideal metaphor for the century's explosive energies. Shimmering on the Bay of Naples is the "emblem of all the forms of wholesale death: the deluge, the great conflagration … but also of survival, of human persistence." Seeking "their ration of apocalypse," visitors from Goethe to Archduke Joseph scale Vesuvius to stare into the active abyss. Naples, nestled beneath the shadow of death, "had been added to the Grand Tour."

Congregating under these skies are gentlemen tourists, sexual exiles, volcano pilgrims, an opera house replete with a "continual ravishment of castrati," and a King of the Two Sicilies who doesn't speak Italian. In this third-largest city in Europe, courtly love takes on new meaning. Sexual excess, domestic spying and sport as bloodbath amuse the Bourbon monarch and his wife, sister of Marie Antoinette. Attending them is the "envoy of decorum and reason," Sir William Hamilton, British Ambassador to Naples. Scholar, courtier, aesthete, "Il Cavaliere" is a familiar Sontag saturnine personality. (Betraying "the hyperactivity of the heroic depressive," he "ferried himself past one vortex of melancholy after another by means of an astonishing spread of enthusiasms.") Thanks to his wife, an asthmatic, harpsichord-playing heiress, he collects treasures. Etruscan vases, cameos, intaglios, shards of lava from nearby Pompeii are sold to the British Museum.

Long mistaking his "capacity for detachment … with his temperament," the Cavaliere civilizes his passions into inanimate objects. At home after his wife's death, though, he meets the 19-year-old, auburn-haired mistress of his nephew Charles. A favorite of the painter Romney, Emma has a less decorous past as a model, including a semiclad stint for a doctor curing couples of impotence. Charles, in need of his own heiress, offers Emma to his widowed uncle, some thirty years her senior. He studies the artifact of his desire. The "small receding chin, the blush of eczema on her elbows … the stretchmarks of pregnancy" are all overlooked. For the true collector, "an object is not sullied…. What counts is that it has reached its destination, been locked into the circle of possessions of the one who most deserved to own it." Emma is shipped to Naples.

Nowhere is Sontag's ironic eye more merciless than in viewing the sexual politics of instruction. Dispatching a battery of tutors to his household, the Cavaliere admires Emma's nimble intelligence as she quickly masters French, Italian, botany and music. Like his pet monkey, Jack, she displays a keen talent for pleasing, one of the many strategies of charm Sontag inveighs against as the social destiny of women. Yet in playing Galatea to his Pygmalion, Emma upends the myth: From her niche in his "gallery of living statues," she steals the limelight. Donning white tunic costumes, she assumes a succession of theatrical poses—Niobe, Medea, Dido, Ariadne. These "Attitudes" soon make her a court favorite, indispensable confidante to the queen. The volcano lover marries his demimondaine. He collects, she performs. Together, their lives affect "poses that excited the greatest admiration."

The collector's public need to admire and be admired is what fatefully links the Hamiltons and Lord Nelson. When the commander of the British fleet arrives for the naval blockade of Naples, the trio find themselves "united in feeling themselves actors in a great historical drama; saving England, and Europe, from French conquest and from republicanism." Three's not a crowd; it's a collection. An "ideal enabler," the Cavaliere lends the hero of the Battle of the Nile his friendship and, ultimately, his wife. As the Cavaliere hoards his treasures, Nelson his honors and Emma her pleasures, each becomes locked in the curio cabinet of the other's vanity and affections. Vesuvius erupts. Jacobins conspire in Naples. The court watches Emma perform her antique Attitudes.

Sontag's considerable achievement in The Volcano Lover is that she's managed to create real characters, not Ideas in eighteenth-century button-and-muslin dress. As admirable, she's made history itself a living character. The first half of the novel is leisurely devoted to the Cavaliere and Emma. The second is a fast-paced, compulsively readable roll call of history: the fall of the Bastille, the Terror of 1794, the 1799 Bourbon exile negotiated by the Hamiltons and Nelson. The trio's fate is intertwined with the Continent's historical destiny. As French troops storm Naples, Nelson commandeers the British fleet, squiring the royal exiles to Sicily. The "Kingdom of cinders" is set ablaze, not by the volcano but by the wholesale slaughter of artists, intellectuals and political sympathizers. Offshore, adrift from history, the trio fiddle while Naples burns.

It was the time, we are told, when "all ethical obligations were first put up for scrutiny, the beginning of the time we call modern." While Sontag rues the spirited naïveté of the enlightened republicans, The Volcano Lover scorns the tyrannies of mob rule, even if that mob is only three lovers. Sontag locates the political in the telling specifics of character. The Cavaliere waits out the French menace by reading his favorite author, Voltaire. With Gallic disinterest, he evacuates his priceless collection with the skill of Napoleon. When his cargo of antiquities is sunk, the only box salvaged is a coffined admiral en route to England for burial. This ironic event, of course, foreshadows Nelson's recall to England, chastised for being private yacht captain to the royal exiles.

In Naples, the restored Bourbon queen erects a Greek temple in gratitude. Entombed inside are smiling wax effigies of the trio. In the highest tradition of historical romance, Sontag has breathed life into these waxworks. Her skill as a novelist is in evoking both our sympathy and our horror at her protagonists' monstrous self-absorption. Each is culpable. Identity, she implies, is never co-authored. For this, Sontag deprives them of their names (throughout, Hamilton is referred to as "the Cavaliere"; Emma, "the Cavaliere's wife"; Nelson, "the hero"). Public scorn singles Emma out as scapegoat. Like Eleanora de Fonseca, unsung heroine of the republic, and even the queen herself, Sontag sees each as punished for having stepped outside the spheres of feminine influence. (Perhaps most treasonous for a woman, Emma gets fat and loses her famous beauty.)

Yet history is effaced to anecdote—Hamilton remembered as the complicit cuckold; Nelson as the vengeful tyrant, wreaking final terror on Naples; Emma as court favorite dying destitute in France after Nelson's death at Trafalgar—and Sontag underlines this with an idea from On Photography: how the mass proliferation of objects helps fragment existence and erode meaning. In suggesting the collector's and lover's acquisitive relationship to the world, she exploits fine narrative details: Emma wearing Nelson's name sewn into her hem; the Cavaliere, first owner of the priceless Portland vase, allowing Josiah Wedgwood to mass-reproduce it; Nelson lending his profile for "candelabra, vases, medallions, brooches."

Sontag's meditations on objects extend to those of erotic desire. Is the love affair a work of art? An original? Or do the repetitions of body and spirit mass-produce emotions, therefore rendering them subject to cliché? "The soul of the lover," she writes, "is the opposite of the collector's. The defect or blemish is part of the charm." Literally. Among the novel's more memorable scenes is Emma kissing the stump of Nelson's right arm; him lovingly viewing her bloated body with his only good eye. In a Sicilian garden of grotesqueries, Nelson plays Mars to Emma's Venus. Alone in a nearby chapel, the Cavaliere is grateful for being in the orbit of their friendship. While the novel is a rich conjugation of connoisseurship—art, women, politics, relationships—at its core is the lesson of "Against Interpretation": the ultimate uniqueness of an object, feeling or person.

With the Cavaliere as the novel's sympathetic lens, The Volcano Lover also plays with the shifting nature of perceptions, the constant, perhaps inevitable, disjunction between experience and memory. Sontag opines: "You project onto the volcano the amount of rage, of complicity with destructiveness, of anxiety about your ability to feel already in your head." Inner peace, like the volcano itself, cannot be collected. Like Pliny the Elder, to whom he compares himself, the Cavaliere is obsessed by the image of Vesuvius erupting in 79 A.D.: "the fearsome noise, the cloud in the shape of an umbrella pine, the death of the sun, the mountain burst open … the rat-grey ash." It is this image that haunts him as he observes the final eruption of the self, his own death.

In grappling with what constitutes the heroic ("And strange, too, seeing the hero in reverse. From another view, the view of history"), Sontag probes its contradictory images in painting. Romney loves Emma's cockney gusto; Elizabeth Vigée-Lebrun loathes it. Reynolds prefers the scholarly Cavaliere as idea of hero to the bony angularity of Nelson. And so she probes how each age, classical and modern, needs to see itself through art. In the eighteenth century, "it showed people able to maintain decorum and composure, even in monumental suffering." Yet today, "the significant moment is the one that disturbs us most."

To that end, Sontag uses a cool cinematic lens to show—and make us feel—moments of ultimate suffering. Chief among those is the gallows scene in which Eleanora de Fonseca is jumped upon, her neck broken, as she hangs alive. Suffering is often best shown in the novel's cameo roles: Baron Scarpia, the black-cloaked police spy of Tosca ("To the wicked, a person understood is a person manipulated"); the Neapolitan duke who is savagely tortured, his collection of Titians and rare books burned by a mob suspecting him of Jacobinism.

One finishes The Volcano Lover certain of its inevitability. It seems a novel Susan Sontag was destined to write, a shift from the moral intelligence of the essayist to the intelligent heart of the novelist. To her admirers, the novel will only confirm her originality, and perhaps win over a whole new set of readers. For The Volcano Lover is not just a thinking woman's (or man's) historical romance but a sly, luminously insightful, provocative novel.

Like Henry James in that other novel on collecting, The Portrait of a Lady, Sontag works the connections between travel, place and desire. In that same sundrenched landscape of southern Italy in which he set Isabel Archer reflecting on art, marriage, women and fate, James asked:

Where, in all this … was the element of "horror"…. What obsession that was not charming could find a place in that splendid light, out of which the long summer squeezes every secret and shadow? I'm afraid I'm driven to plead that these evils were exactly in one's imagination, a predestined victim always of the cruel, the fatal historic sense. To make so much distinction, how much history had been needed! So that the whole air still throbbed and ached with it, as with an accumulation of ghosts.

In The Volcano Lover, Susan Sontag illuminates that fatal historic sense, its secrets, its shadows, through the ghosts she's brought back to life.