"I like purple passages in my life," Muriel Spark once told an interviewer. "I like drama. But not in my writing. I think it's bad manners to inflict a lot of emotional involvement on the reader - much nicer to make them laugh and to keep it short." Although Spark was not averse to playing cat and mouse with those who sought to encapsulate either her or her work in a neat paragraph or two, this self-summary is telling. One may counter that there is plenty of drama in her novels, from corrupt nuns to fatal conflagrations, from mysterious charismatics to outright deceivers, but they all work on the principle of control and distance, on the absence or subversion of emotion in the most overwrought of circumstances. What, though, of her life?

Martin Stannard's exhaustively researched biography, a decade in the writing and encouraged by its subject before her death in 2006, does not shy away from the purple passages, but steers a careful course to ensure that full-blown melodrama is avoided. Amid the multiple flights, bust-ups, triumphs and disasters that stud Spark's life, he emphasises her need to find space, quiet and isolation - her "island" - in which to write. Work was everything; the rest was part of a pageant that was amusing for as long as it didn't distract.

Space and quiet were not commodities readily available in her early years. Born Muriel Camberg in 1918, the daughter of a Jewish mechanical engineer and his gregarious gentile wife, she grew up in a shabby-genteel flat in Edinburgh that brimmed with lodgers, stray family members and passers-by. At Gillespie's school she encountered an inspirational teacher who became the model for the fearsome Jean Brodie and who really did refer to her charges as the "crème de la crème", learning from her, in Stannard's words, "a nascent scepticism about all systems of power and their potential for corrupting free will".

The process of separating herself from her upbringing had begun, provoking the first of many self-exiles. In 1937, when she was 19, she left Scotland for Southern Rhodesia with a maths teacher, Sydney Oswald Spark, marrying him shortly after. Their wedding night, Spark said later, was "such a botch-up". By the time their son, Robin, was born, one year later, Ossie was already in severe mental breakdown. It was time to escape again.

That escape took some years to effect, and was achieved only by leaving Robin behind, but eventually Muriel arrived in the more convivial milieu of mid-40s London. Stannard conjures the febrile atmosphere of the capital and the energising effect it had on his subject, who found herself engaged in Foreign Office propaganda campaigns, dining in hotels with married men and entering the literary world by becoming the general secretary of the Poetry Society. This period, which provided her with two serious lovers, Howard Sergeant and Derek Stanford, and was to end in a vicious power struggle ("You have always had a strange complex about your 'importance'," said one of her opponents at the Poetry Society), confirmed Spark in her own mind as a writer. Stannard gives us Spark's transformation from marginal littérateur to driven, prolific novelist in a detailed, thoughtful fashion, and it is not to his detriment that there remains something of a mystery. There was a mental collapse, fuelled by diet pills, during which she believed that TS Eliot was sending her coded messages through his work; a further distancing from son and family; a final break from Stanford; and her entry into the Catholic church. In a Carmelite priory in Kent in 1957, she wrote her first novel, The Comforters; four more were to follow by the end of 1960.

Spark's spiritual crisis gave her a framework in which to ponder the themes that beset her mind and her work: predestination and free will, the disappearance of an anthropomorphic God and the presence of evil. She aimed for compression and obliqueness. There was, after all, no need for an excess of "emotional involvement", either for the reader or for the writer who, having created her characters, had the same responsibilities as God. The appropriate mode for all this was satiric, comical, playful; not the deadening hand of traditional realism.

Her admirers, Evelyn Waugh, Graham Greene, VS Naipaul and John Updike among them, agreed. Another transformation - into world-famous writer with her own office at the New Yorker (which first published The Prime of Miss Jean Brodie), a string of escorts, diamond rings and even a racehorse - was on the horizon. Stannard details her near-constant wrangles with her publishers with extraordinary patience; one appreciates her talent for hard bargaining without, perhaps, being given chapter and verse over her royalty statements. But if Spark's biographer can appear disconcertingly accepting of some rather self-aggrandising behaviour, he is more compelling on the novels themselves - the vast mental strain of her attempt to confront the fracture between Christianity and Judaism in The Mandelbaum Gate (1965), for example, and the experimentalism of later works such as The Driver's Seat (1970) and The Hothouse by the East River (1973) - and on her determination to keep moving, from New York apartment-hotel to Roman palazzo, from friendship to friendship. Her correspondence of the 1960s, he writes, "suggests her expectation of betrayal, as though she were eager to detect it in order to relieve herself of the burden of intimacy".

Spark was unsentimental about betrayal; it was, she felt, unrealistic to expect loyalty, which didn't stop her outbreaks of fury (often described rather euphemistically by Stannard as "irritation"). Late in her life she found a measure of tranquillity with Penelope Jardine, the companion who acted as secretary, major-domo and confidante, although probably not, despite frequent surmise, as her lover. The novels - including the wonderfully semi-autobiographical A Far Cry from Kensington (1988) and Aiding and Abetting (2000) - did not stop coming. The latter, a jeu d'esprit that juxtaposed a revived Lord Lucan with a fake stigmatic psychoanalyst, was a brilliant éxposé of the lies we are prepared to tell ourselves in order to survive, of the deceptive texture of everyday life. As one of the characters in her play Doctors of Philosophy noted, "reality is very alarming at first and then it becomes interesting".

 This article was amended on 17 August 2009. The original referred to jeux d'esprit. This has been corrected.

"Lucrezia Borgia in trousers" was how Muriel Spark once described herself. She certainly knew how to strike fear into the heart of anyone who threatened her artistic vocation or obstructed the strict control she had established over her life and reputation. Publishers who rewarded her with paltry advances and minuscule publicity were excommunicated. Former lovers who betrayed Spark found themselves consigned to an outer ring of hell. Robin, her only child, was excluded from her will after a dispute in which he claimed that his mother had denied the truth about her Jewish origins. Even writers and critics applying to confirm a few shards of biographical detail were dismissed as "intrinsically insolent".

If Martin Stannard was ever at the receiving end of this kind of treatment, he's keeping tactfully silent about it. Appointed Spark's official biographer in 1992, he appears to have encountered problems only when his subject began to read his typescript. At one stage before her death in 2006, Spark was said to have been negotiating the text of the book with her biographer line by line, leaving Stannard to admit publicly that publication of the biography was by no means definite.

Muriel Spark's resistance to a rigorous biography is scarcely surprising. Her novels never fail to provide the reader with a mass of circumstantial detail, but offer few clues to her characters' motivations. Similarly, Spark's one serious venture into autobiography, Curriculum Vitae, covering the 39 years to the publication of The Comforters, her first novel, is as bald a summary of her life as its title makes it sound. Given this, Stannard is to be congratulated on producing what will undoubtedly be the standard biography of a writer with perhaps the most distinctive voice  darkly satirical with theological dimensions  in postwar British fiction.

Sceptics may ponder the traces of Spark's interfering hands: for instance, in the narrative of her escape, in 1944, from Africa and a violent, possessive husband, the desertion of a young son is presented as an act of sweet reasonableness rather than a desperate last resort.

However, the overriding impression created by the book is of fair judgments. The contents of Spark's voluminous papers may be largely anodyne. But to compensate, Stannard has dug up other documentation and testimony, interviewing Spark's brother, Philip, about their Edinburgh childhood, dominated by the twin matriarchy of mother Cissie ("a ramshackle galleon") and maternal grandmother Adelaide (a valkyrie-like figure who boasted of the Jewish blood that had made her so clever); and locating the letters to Spark from one postwar love interest, Howard Sergeant, which testify to Muriel's potent sexual allure in her smart, sassy 30s.

The first half of Spark's story would be a gift to any biographer and Stannard makes the most of it, in sharp contrast to his treatment of her later life, which tends to take on the precision of an appointments diary. Transfigurations are the essence of Spark's art. But the most remarkable change occurred not in her writing but in her life, as the plump, working-class girl from Edinburgh became an international celebrity, at home in New York and Rome, decked out in diamonds and owner of a racehorse purchased from the Queen.

It's a true rags-to-riches tale. Spark's father, Barney Camberg, was a mechanical engineer. His parents were Russian Jews. At the age of five, in the summer of 1923, Spark started her formal education at James Gillespie's school. Here she remained until she was 16, when she left to take a course at Heriot-Watt University in business English, establishing a student reputation as a poet and having the good fortune to come under the influence of several remarkable teachers, including Christina Kay, the model for Jean Brodie. Unlike Brodie, Kay reportedly possessed a heavy moustache, but more reminiscent of her fictional counterpart, she admired Mussolini, taught by "dazzling non-sequiturs" and once held up a photo of the overweight Muriel to her class and declared: "You can see the sensitivity in that line of Muriel's arm."

In 1937, a disastrous marriage to Sydney "Solly" Spark, an older man with serious mental problems, led Muriel to Southern Rhodesia, where Solly was a teacher. Here, she wrote a series of stories moulded by the chaos and violent unreality around her. Back in Britain, having left her husband, Spark honed her comic voice by taking a job in political intelligence, working in a kind of department of dirty tricks and broadcasting misinformation to Hitler's troops. Later, as general secretary of the Poetry Society, Muriel crossed swords with Marie Stopes, the birth control campaigner, and found herself lamenting that Stopes's mother had not been better informed on the subject.

Spark never forgot the poverty of the next 12 years, eking a living from her writing, accepting multiple commissions from cheapskate publishers while living in bedsits with barely enough to eat. This is the world of her last great novel, A Far Cry From Kensington, a revenge comedy, as Stannard rightly calls it, in which Spark finally gets her own back on Derek Stanford, once her collaborator and lover.

During the breakdown she suffered in the mid-1950s, brought on by a dependence on diet pills, Spark believed (not without justice) that Stanford was filching her papers and trying to steal the mystery of her genius. She emerged from this collapse strengthened by her conversion to Catholicism. This is an area about which Spark had little to say in her autobiography, but which Stannard makes clear was partly the key to her success as a writer, and instigated the independent, rootless existence Spark was to pursue to her final decades. Henceforth, she saw no contradiction between her artistic and spiritual vocation. "Both required an act of faith, of renunciation, disaffection."

That "act of faith" produced an extraordinary 22 novels and worldwide fame, profitably enhanced by stage and film adaptations of Brodie (with the theological overtones of the novel trimmed by screenwriter Jay Presson Allen). But the accompanying acts of renunciation and disaffection were ultimately responsible for something much less benign and one reaches the end of Stannard's biography with the depressing realisation that the passion this independent, supremely confident woman felt for her art was simply not matched by feelings of similar intensity for any other human being.