There are always two to a talk, giving and taking, comparing experience and according conclusions," Robert Louis Stevenson wrote in an 1882 essay. "Talk is fluid, tentative, continually 'in further search and progress.'" Biographer Claire Harman seizes on this passage from "Talk and Talkers" and appends the rhetorically incomplete response, "To be continued." The device allows her to underline the vexed sense in which a lack of completeness resides at the core of the life and work of the curious Scottish writer.

"The pleasure in writing the beginnings of stories (natural enough in an apprentice) and a revulsion from the work involved in finishing them would remain the most marked characteristics of Stevenson's creative life," Harman writes in Myself and the Other Fellow: A Life of Robert Louis Stevenson. As she sees it, a thoroughgoing sense of unfinishedness goes hand in hand with a theme permeating the writer's oeuvre—the split self and its familiar counterpart, the double, a leitmotif not just in Stevenson's best-known tale, that of Dr. Jekyll and Mr. Hyde, but also in any number of his works, especially the nocturnal miscreant of Deacon Brodie, the Raskolnikovian killer in the short story "Markheim," even the pairing of innocent Lowlander David Balfour and exiled Highlander Alan Breck in Kidnapped.

The most cursory glance at Stevenson's life has one seeing double—or if not paired things, then polarities that sort of but don't quite add up to a whole. A sickly apparition of a man, Stevenson spent the greater part of his time far away from his native Edinburgh in what looks on the surface like a quest for ultima Thule but was in fact a bid simply for a wholesome, sunny environment where he could regain his health. It would be an affront to the spirits of Noah Webster and Edward Said to call him an exile, but in certain respects he was.

His best attempts at rivaling Sir Walter Scott in writing the great Scottish novel, The Master of Ballantrae and Weir of Hermiston, were undertaken in the most un-Scottish locales of the South Seas and Samoa, where he lived out his days with his American wife, Fanny Stevenson. His appearance too was hard to reconcile: Even at his heartiest, he looked like a grossly elongated ephebe—pale, half man, half child, with long, greasy locks atop a beanpole figure in a dandy's velvet coat. And if he labored after an adult readership and literary respect, his most successful work was of course that nominally written for young readers—Dr. Jekyll and Mr. Hyde, Treasure Island, and Kidnapped, as well as A Child's Garden of Verses. His facility with the adventure genre suggested nothing less than a child trapped in an adult's body, a boy who never grew up. Even in the production of his work, as lonely as writing can be, he sought out others: He entered into literary collaborations throughout his life, whether with his friend William Henley on Deacon Brodie or with his stepson, Lloyd Osbourne, on The Ebb-Tide. As Harman points out, he was even ambidextrous.

Over the years RLS has attracted no shortage of biographers. Harman's is the third since 1993, in addition to Alberto Manguel's lean Jekyll-ish novella Stevenson Under the Palm Trees, which drew heavily on the biographical record of the author's waning days in Vailima, Samoa. Since the first accounts of Stevenson's storied life began to appear just after his death, in 1894, he has become the rare writer whose literary afterlife may eventually reside in the limbo (purgatory?) of the biographical genre. It isn't really hard to see why.

Born in 1850 to a family of distinguished engineers with a history of mental instability—his grandfather Robert had accomplished the nearly impossible feat of constructing the Bell Rock lighthouse off the northern Scottish coast—Stevenson was raised as a lonely valetudinarian by his nanny, Allison ("Cummy") Cunningham, who soothed the boy's frequent night terrors by regaling him with tales of eternal damnation and treated his fitful insomnia by encouraging him to down large quantities of black coffee. (He would later dedicate A Child's Garden of Verses to her, calling her "my first wife.") Cummy's stories of sinners' hells were familiar to the young Stevenson—his father, in addition to being a man of science, was a staunch, disapproving Calvinist.

In more ways than one, RLS failed to follow in his father's footsteps: "The marrow of the family was worked out," he wrote in the third person in "Autobiographical Note," "and he declined into the man of letters." Young Stevenson's ambition to become a "slinger of ink" was galling enough for the nose-to-the-grindstone clan, but his lack of faith—and private admission of as much to his father in 1873—finally effected a break with the elder Stevenson (whose response to RLS's admission was, "You have rendered my whole life a failure") and the upright Scotland he represented.

But 1873 would be momentous for other reasons for Stevenson—it marked also the real beginnings of his peregrinations, south to Suffolk, east to bohemian France and Davos, Switzerland, and eventually to California, Hawaii, and Samoa; and the first of his two tortured love affairs with older, married mother figures. (The second, with Fanny, in fact led him in 1879 on a nearly fatal transcontinental trek to California, although he did finally persuade her to dump her low-life husband.) And it could be considered the decisive point at which he embraced his desire to write.

So many false starts, breaks from the family and the homeland, and rather pathetic attempts at achieving "oneness" frantically pinned on others, particularly on women in troubled, unhappy marriages. The late Romantic hero is either, depending on your tastes, a tragic throwback or (more often than not) a cloying cliché. At least for some time after the author's death, the weight tilted more and more toward the latter, and by 1948, Graham Greene (a remote relative of the Scots writer) could grouse:

His comparatively uneventful life (adventurous only to the sedate Civil Service minds of [Stevenson's literary executor Sydney] Colvin and [Edmund] Gosse) was magnified into a saga: early indiscretions were carefully obliterated from the record, until at last his friends had their reward—that pale hollow stuffed figure in a velvet jacket with a Lang moustache, kneeling by a chair of native wood, with the pokerwork mottoes just behind the head—'to travel hopefully is a better thing than to arrive,' etc., etc.

What sparked Greene's grouchy ire was the evisceration of Stevenson the novelist before the myth of Stevenson: the puppet RLS, sprig of heath peaking out a wee mickle from the pocket of his velvet jacket, could be nothing less than nauseating, no less in the graceless hands of ineffectual biographers, with their feigned intimacy of a sort of Boy's Life life led by a charming (but harmless) spinner of yarns. The problem, though, with Greene's complaint is that Stevenson always invites this easy intimacy in his writing, whether in the early travelogues and young adventure tales or the literary essays and later novels of Scottish history. Even his friend Henry James wrote, "To read him—certainly to read him with the full sense of his charm—came to mean for many persons much the same as to 'meet' him. It was as if he wrote himself outright and altogether, rose straight to the surface of his prose, and still more of his happiest verse."

To be sure, Harman does much more than present the "pale hollow stuffed figure." She diligently tries to let the various contradictions that made up RLS breathe through her well-researched biography, as well as to account for why, as James further put it, "Stevenson never covered his tracks, and the tracks prove perhaps to be what most attaches us." It's tempting to say that Stevenson never covered his tracks because he was never that sure who he was either, and many of the letters he wrote provide in particular a sense of how he seemed at times to live outside himself. "Stevenson was rather fascinated by the spectacle of himself in love," Harman writes, "and at times asked [his first love] Mrs. Sitwell for copies of his letters to be sent back, for him to work into possibly saleable prose." Harman's book begins with an episode in which Stevenson fills out the questionnaire in a pamphlet written by eugenicist Francis Galton that purported to forecast the abilities of the reader's future offspring on the basis of data about his or her ancestors. (Quotations from the pamphlet provide Harman with the epigraphs for each chapter as well.) The gloomy air of pre-Freudian "psychology" is an apt environment for RLS and his never truly quenched ability to know himself.

Others have written at length on "doubleness" and Stevenson, including Karl Miller and Wayne Koestenbaum, who examined the particularly homosocial exchanges of the collaborative work of RLS. Harman doesn't slight these sources, but she doesn't seem particularly interested in them, either. Her biography would have benefited from presenting a more culturally wide-ranging approach to the double in the late nineteenth century and being a bit more patient with academic approaches, especially to queerness in Stevenson. Still, her readings of RLS's literary prose are critically strong—she makes a compelling case especially for a few lesser-known stories—and one begins to see how Stevenson's anxieties illuminate even the travel writing (it's impossible to reread the charming Travels with a Donkey in the Cévennes, Stevenson's most desperate attempt to escape the company of others, without sensing his companion she-ass, Modestine, as somehow a mute extension of the writer). At the end of Myself and the Other Fellow, we somehow know Stevenson that much better, even as we begin to lose a sense of exactly who he was.

Eric Banks is editor in chief of Bookforum.