entering her middle years, Madame de Pompadour confided to King Louis XV of France that she'd never actually enjoyed sex that much. The king deferred to her wishes: Pompadour retained the title of official mistress, but instead of sex, the couple shared the reports compiled by the Paris vice squad. The Paris police were skilled in surveillance, and some years later one of their highest ranking officers was specially assigned to the Marquis de Sade. Before Sade ever became a pornographer, then, he was an unwitting pornographic content provider for the king of France.

Power, publicity and pornography were as intimately linked in Sade's times as they are in our own -- but even within this context, Sade (1740-1814) was scary and special. It's not that he was more violent than other libertine aristocrats, for flagellation and sodomy were common tastes. As for his most sinister episode -- hiring some half dozen adolescent servants and forcing them to participate in a series of orgies -- well, this was an era when the comte de Charolais used to shoot common people for sport and was repeatedly pardoned for it by the king.

But Sade had the kind of bad attitude that always gets attention. He was strange, cold, deliberate: One prostitute reported to the police that he'd forced her to stay up all night listening to anti-religious poetry. While most libertines indulged themselves at wild parties or used the services of procurers, Sade and his valet cruised the streets, assembling casts of prostitutes to drill through tightly scripted, episodic scenarios. He liked sex toys, costumes and props, especially religious items -- he'd masturbate with crucifixes, shit into chalices. Shocking himself by exploiting powerful symbols, he also shocked much of France and became, himself, a symbol. All in all, he would be incarcerated for more than 27 of his 74 years (half of these at the end of his life, under Napoleon).

The years of incarceration -- combined with the bad attitude writ huge in his pornography -- have contributed to Sade's reputation as ultimate rebel and martyr to sexual and intellectual freedom, particularly among the writers of poetic manifestos. But those who admire him as a rebel miss some pretty obvious points: that he rebelled against the limits of his already extensive class privilege, and that his lack of concern for the prostitutes and other lower-class people he forced to act out his fantasies can't be interpreted as a blow for anybody's freedom. On the other hand, his detractors (who see him as a monster best locked up) don't seem to care that he caused no serious physical injury -- and they may well celebrate the fact that he was incarcerated for the last 13 years of his life solely for writing pornography. Better to turn, then, from the self-serving abstractions of the manifestos to the extravagant and compelling facts of the life -- Sade "at home," as Francine du Plessix Gray presents him in her consistently entertaining biography.

Donatien Alphonse Frangois de Sade was related to the Bourbons on his mother's side and descended from ancient Provengal nobility on his father's. The Sades were arrogant about their lineage. An ancestor, Laure de Noves, may have been the Laura to whom Petrarch dedicated his famous sonnets; with rather less evidence to go on, the family also claimed descent from the Magi. But by the second half of the 18th century they were bankrupt, Sade's father having squandered their fortune and reputation through a set of extravagant dalliances and diplomatic misadventures. As gifted as his father at making powerful enemies, Sade was exiled from court at the age of 4 for hitting a young Bourbon prince who'd taken one of his toys. By his 20s, he had a bad reputation as a rake, and probably more seriously, no friends in court circles -- when invited to hunt with the king, he took pride in not showing up.

So, when Sade began being arrested for mistreatment of prostitutes -- and appearing in the king's dossiers -- he had nobody to get him out of trouble except his wife's family. Only recently ennobled, the prudent, upright Montreuils had been the best connection the financially strapped Sades could come up with on the marriage market. Monsieur de Montreuil's father had amassed considerable wealth as treasurer of a few prosperous northern towns; Monsieur de Montreuil himself was chief judge of an important Parisian court. Typifying bourgeois stability, competence and energy, and busily marrying into the aristocracy, they were a family on the way up (while the Sades were on the way down). "I pity them," Sade's father wrote to one of his sisters before the wedding, "for making such a bad purchase."

Still, the Montreuils, particularly the formidable mother-in-law, Madame de Montreuil, did their best to keep Sade out of trouble, writing letters and paying off complainants. They might have done so forever had Sade not seduced his wife's beautiful younger sister, the family's most cherished child and best chance for a brilliant marriage connection. After that, all bets were off, and in 1778, Sade was arrested and locked away for 12 years by lettre de cachet, or warrant of the king, without trial, sentence or even accusation. It was only the French Revolution that freed him, all lettres de cachet being nullified by 1790.

Gray, an acclaimed novelist and biographer ("Lovers and Tyrants," "Rage and Fire: A Life of Louise Colet"), tells the story with energy and intelligence. She delineates Sade's intimate, even complicitous, relationship with his wife, Renee-Pelagie de Montreuil, and paints a subtle, balanced picture of Renee-Pelagie's powerful mother. Deeply in love with her husband, Renee-Pelagie willingly put up with all sorts of demands, some sexual, some ruinously expensive -- as, for example, when Sade organized his family into a theatrical troupe, hired some dozen additional professional actors, curtain-pullers and wigmakers and shuttled the whole ill-assorted crew every few days over some of Provence's roughest terrain in order to present 19 plays in two venues to local gentry who mostly stayed away.

My own favorite turn to the narrative follows the middle-aged Sade, newly released from prison, during his brief career as a revolutionary apparatchik. Signing up as an "active citizen" of his Paris neighborhood, "Citizen Louis Sade" (he'd always wanted to be named for the kings of France) joined committees, took neighborhood watch duty and helped rebaptize streets with names like "Rue du People Souverain." For a penniless ex-aristocrat who privately believed in constitutional monarchy and deplored capital punishment, this was clearly a survival tactic; what's notable, though, was how good he was at it. He became official scribe of his district; his reports, adorned with phrases like "the great republican family we have just founded," were circulated as models of patriotic rhetoric. And in 1793, as secretary of his section, he put himself at considerable risk in order to save Monsieur and Madame de Montreuil from execution.

Gray is equally good at fine distinction and delicious detail: After deftly explaining the ancien rigime's confusing dual legal system, she also takes the time to inform us that the aphrodisiac Spanish fly was, in fact, made from Spanish flies (well, "Mediterranean insects," anyway). Still, no matter how compellingly Sade's story is told, no matter how recherchi its details, it will always pale beside those other stories -- the unique, monstrous pornographic fictions he wrote -- which are, finally, why we remember him at all.

Sade only began to write pornography in prison, and it was only in prison and on paper that he began to give his obsessions suitable form and adequate scope. "One moment," a character exclaims at the beginning of "Juliette," "one moment, my dears, we had best introduce a little method into our pleasures' madness; they're not relished unless organized." And so it continues, each deed, each pleasure, each outrage is relentlessly organized, enumerated, choreographed. Some 500 pages later, when Juliette and her mentor Clairwil are fucked repeatedly and symmetrically by 64 well-endowed Carmelite monks ("we took on our men in groups of eight"), Sade appends a helpful footnote toting up the penetrations, thus saving his reader the bother of doing the math herself. There are, after all, nearly 700 pages for "your instruction, your sensations, and your happiness" yet to go.

Sadean sex is best done in Busby Berkeley-like production numbers, cavalcades of mechanical intercourse, pageants of incessant horniness. The episode with the monks, dispatched in neat octets, resembles a computer algorithm, an endless loop that defies both exhaustion and satisfaction. Locked in prison, deprived of actors for his fantasies, Sade conducted thought experiments, built worlds of libertine domination and devised theaters of cruelty where he finally got to play all the parts.

Which isn't to say that his work is always fun to read. The crimes committed in "The 120 Days of Sodom" are unreadably brutal; the redundant disquisitions on nature, sex and crime that appear everywhere in his work are brutally unreadable. The author whom Apollinaire famously (and fatuously) called "the freest spirit who ever lived" was rarely free enough of his visions to give them accessible shape. But when he hits a groove, he's uniquely funny, lucid, sardonic. "Justine," as Angela Carter pointed out, is a satire on so-called virtue's inability to see beyond itself: The book's perpetually beleaguered heroine is as incapable of learning from experience as Wile E. Coyote.

The Age of Enlightenment was also a great age of pornography. The pornographic works smuggled into France were called "philosophical" books, because they typically interspersed bawdy scenes with speeches based on materialist doctrine that challenged religious -- and therefore contemporary political -- authority. But Sade turbocharged the genre, lacing it with torture and murder, and raising the philosophical ante. Strip away the moralities and idolatries, Sade proclaimed, and what you'll discover in your lonely, implacable desires for power and pleasure is nature in all its cruel anarchy.

Roland Barthes called Sade's fictions "utopias." He meant impossible, rather than ideal, societies: exuberantly constructed models of rampant power that can only exist as fiction. Minutely conceived in its mores, its rituals and costumes -- even its menus -- the world of Sade's novels is a purely imaginary system, like a perpetual motion machine. There's no real communication in Sade: His libertine masters of the universe simply lecture us, their victims and each other, while the victims are often mute. Barthes calls our attention to a particularly hideous Sadean invention: a headpiece that transforms its wearer's screams into the lowing of a cow. No wonder Sade is Andrea Dworkin's ideal pornographer. For Dworkin, Sade isn't a fantasist at all, but patriarchy's ultimate gonzo journalist, a whacked out, tell-all chronicler of male domination.

But whatever Sade's porn is like, it's clearly nothing at all like today's S/M scene, in which scrupulous attention is paid to procedure and consent, power is "exchanged" and communication is, if anything, micromanaged. The contemporary S/M ethos demands communication in extremis between dominant and submissive, shared understanding of limits and elaborate negotiation beforehand about permissible activities. Written contracts can be helpful, S/M pundit Pat Califia suggests -- for example, "around work issues," to head off problems with an insensitive dominant who'll phone you in the middle of a staff meeting to demand praise, or a selfish submissive who expects to be corrected just when you're rushing to finish this month's payroll.

Two hundred years after Sade wrote his fictions, his name (along with Leopold von Sacher-Masoch's) graces a spectrum of behaviors ranging from gourmet recreation to identity subculture. You can sharpen up your technique at workshops, share your feelings at a support group or get pointers from books like "Bondage on a Budget" or "Exhibitionism for the Shy." A friend sent me an article on London S/M clubs clipped from an in-flight magazine; an S/M bed and breakfast in the Bay Area bears the tastefully P.C. name of "Differences." And at last year's San Francisco Gay and Lesbian Freedom Day Parade, I saw a leather-clad contingent marching beneath a flag with black and blue horizontal stripes and a red heart in its upper left-hand corner. The cozy groupiness of it all is anathema to Sade, but I think he might have recognized the humor -- and certainly the passions for costume, symbol, scripting, control.

But the furious, infantile selfishness of his pornography is, and always will be, something else. Barthes speaks of Sade's "happiness of writing," the unbounded pleasure of pure all-systems-go elaboration, of kaleidoscopic world-building. I read him with alternating disgust and hilarity and with consistent amazement. Manic, cartoonish, cruel, intractable, absurdly energetic and redundant, yucky -- the totality of the work can't be deduced from the life, though the life, told so well by Gray, provides an excellent angle of vision on the work. There's really no feeling "at home" with civilization's most outrageous malcontent, but Gray's biography brings us a bit closer.