Not many writers furnish enough material for a biography focused entirely on their love lives. In his short life (1788-1824), George Gordon, Lord Byron, managed to cram in just about every sort of connection imaginable—unrequited pinings galore; affairs with aristocrats, actresses, servants, landladies, worshipful fans, and more in almost as many countries as appear on Don Giovanni's list; plus countless one-offs with prostitutes and purchased girls; a brief, disastrous marriage; and an incestuous relationship with his half-sister. And that's just the women! It's a wonder he found the time, considering everything else on his plate. He composed thousands of pages of dazzling poetry, traveled restlessly on the continent and in the Middle East, maintained complex relationships with friends and hangers-on, wrote letters and kept diaries and read books constantly, boxed and took fencing lessons and swam, drank (prodigiously), suffered bouts of depression and paranoia and physical ill-health, and, in his later years, joined in Italian and Greek liberation struggles. Just tending the menagerie that he liked to have about him—monkeys, parrots and macaws, dogs, a goat, a heron, even, while he was a student at Cambridge, a bear—would have driven a lesser man to distraction.

At 10, upon the death of his great-uncle, a supposed murderer known as the Wicked Lord (where's Ann Radcliffe when you need her?), he became the sixth Baron Byron and owner of Newstead Abbey, a grand semi-ruin in Nottinghamshire, complete with monkish ghosts. One of the many contradictions in his deeply divided nature was that the world-famous champion of liberty took extraordinary pride in his rank: He was forever commissioning ostentatious furniture with the family crest and motto ("Crede Byron") and stormed out of a dinner party abroad because local protocol demanded that a lower-born diplomat precede him into the dining room.

From an early age, Byron had established what was to be a romantic pattern: "mooning love for cousins" and a neighbor, Mary Chaworth, and sex with varying degrees of emotional intensity—from extravagant passion to callous brutality—with pretty much anyone ready to hand, beginning with Newstead servants of both sexes and fellow students at Harrow and Cambridge. Once the publication of Childe Harold's Pilgrimage made him a celebrity, at the age of 24—"I awoke one morning to find myself famous," he quipped—"the fugue of women," as Edna O'Brien cleverly calls it in her brief new biography, began in earnest.

There was the piquant and capricious Lady Caroline Lamb, who famously described him as "mad—bad—dangerous to know," which is just what he would come to say about her. As his ardor cooled, she became obsessed and vindictive, staging public scenes and persecuting him with letters, sudden visits, and, eventually, a scandalous roman à clef. He escaped Lady Caroline by flinging himself into the arms of Lady Oxford, a powerful free-thinking political hostess and beautiful 38-year-old mother of six. "We lived like the gods in Lucretius," he would say of the seven or eight idyllic months they spent in her country house.But these affairs (and others) paled beside his incestuous affair with Augusta, Mad Jack's daughter, five years older, married, the mother of four, whom he came to know for the first time in London in 1813: "And so it is Guss and Goose and Baby Byron and foolery and giggles, Augusta wearing the new dresses and silk shawls he has bought for her, the thrill of showing her off to the acerbic hostesses, home in his carriage at five or six in the morning ... and somehow it happened, the transition from affection to something dangerous. Never, he said, 'was seduction so easy.' "

Why, given all this excitement, Byron chose to marry Lady Caroline's prim, religious cousin, Annabella Milbanke, is a mystery. Perhaps he hoped marriage would quiet rumors—incest was a bit much even for the cynical Regency grandees among whom he moved. Perhaps it was a gesture of despair, with a bit of fortune-hunting thrown in. In any case, the marriage was a nightmare, beginning with the bridegroom pacing the halls with loaded pistols on his wedding night and culminating in Annabella's departure, newborn infant Ada in tow, after only 16 months. In her legal case for a separation she accused Byron of ongoing incest with Augusta and appalling maltreatment of every kind, culminating in anal rape two days after she gave birth.

Ostracized by those who had lionized him, Byron left England, never to return. Further adventures and abuses followed, the worst of which was probably his cruelty toward Mary Shelley's stepsister, Jane Clairmont, who bore him a daughter, Allegra. Rather than financially assisting Jane in raising the child, which he could easily have afforded to do, he took custody and refused to answer Jane's increasingly pathetic letters begging for news; he soon handed Allegra off to assorted others before sending her to a convent school, where she died, unvisited by anyone but Shelley, at age 5. By then he had settled down with the young, beautiful, married Italian countess Teresa Guiccioli. Tellingly, though, the last love of his life, as unrequited as the first, was for Lukas—a teenager attached to the ragtag army Byron raised in his botched attempt to liberate Greece—who was with Byron at his death at 36 of fever in Missolonghi.

O'Brien relates all this and much else in a headlong sensuous rush, almost like one of her own novels. It's fun to read, but I could have done with more digging and thinking. Unlike Fiona MacCarthy's terrific Byron: Life and Legend, Byron in Love makes little of Byron's homosexuality, which was far more extensive than O'Brien chronicles. For MacCarthy, indeed, his frenetic heterosexuality was due at least partly to British sodomy laws, which carried the death penalty; his passions for women were brief, and his behavior to them cruel and capricious, because he really wanted to be with teenage boys.

O'Brien also, inexplicably, mentions only on Page 186 that at the age of 9 or 10 Byron had been repeatedly sexually abused, as well as ferociously beaten, by his nanny, May Gray: "In the daytime she fed him dire Calvinist sermons, providing an uncomprehending brew of guilt and desire, alternating with scenes of jealousy as she brought home drunken coach boys from Nottingham to carouse with." Whether or not this weird coerced initiation lay behind Byron's frequently expressed sense of lost youth and jaded emotions, it certainly explains why he thought religion was rubbish and women's supposed purity a lie.

It is easy to see Byron as a cad, a narcissist and, at bottom, a misogynist. But that would be unfair. Byron's great insight, in an era where women were expected to be placid and insipid (not that they were!), was to see that women were much like men: They wanted sex and went after it eagerly, if secretly. Don Juan, his great satiric novel in verse, is a virtual catalog of passionate women who are anything but bashful, even if still virginal, and who are presented without condemnation, as human beings doing what human beings do. He understood, too, how limited was women's scope for action. "Man's love is of man's life a thing apart," writes Juan's first love, the married Donna Julia, from the convent to which she is confined when their affair is discovered. " 'Tis woman's whole existence."

Byron's electrifying effect on women readers was inspired not just by his handsomeness, his woundedness, and the exciting hope of reforming him, which was poor Annabella's undoing. It was also due to his frankness, that sense his poetry gave that he understood his reader's secret rebellious thoughts and longings for experience, pleasure, a life beyond tea tables. It wasn't only the Greeks who found in him a champion of freedom.

One final note: O'Brien has little to say about Byron's poetry, but without it, he would be just another eccentric milord. To find out what all the fuss was about, pick up a copy of Don Juan. It's as fresh and sparkling and hilarious and sexy as the day it was published, and will make you wish the author was still around, so that you could write him a letter proposing a discreet assignation.