On the evidence of , a lot of the mystical aura surrounding the killer was less real than imagined by a terrified populace and titillated press corps. But Guinn doesn't buy any cultist mumbo-jumbo. The cover of pointedly features a photo of its subject not as Crazy Charlie, as he sometimes called himself, but as a smiling, suit-wearing, precocious little crook in his pimply years.

Guinn's main thesis is that Manson was a lifelong social predator: "There was nothing mystical or heroic about Charlie - he was an opportunistic sociopath." And in 1967, when he walked out of prison at 32 and began trolling for acolytes in Haight-Ashbury in San Francisco, the culture of national upheaval "made it possible for him to bloom in full, malignant flower". Among the sources for Guinn's account are Manson's sister and his first cousin, and he has even found a schoolmate to describe the abusive teacher who treated Manson harshly in the first grade. By that point, he had already seen his wilful teenage mother sent to prison for her role in a robbery (the assault weapon: a ketchup bottle); she had singled out the victim, she said, because he "had too much money for one man".

Were the seeds of the Manson Family's savage Tate-LaBianca murders sown this early? Guinn thinks so. His punchy style renders the mother's first crime as "an impetuous decision that would affect - and cost - lives over the next three-quarters of a century".

His mother's first conviction steered her young son towards a string of reform schools and prisons, places that shaped his education. He listened to pimps explain how to control women. He read the brand-new teachings of Scientology.

And, in the kind of touch that keeps steadily surprising, Guinn points straight to a link between Dale Carnegie's to Manson's methods of persuasion. Among one of Carnegie's lesser-known statements: "Everything you or I do springs from two motives: the sex urge and the desire to be great." Manson clearly took that and "Begin in a friendly way" to heart.

In a book that pays insightful attention to context, Guinn juxtaposes Manson's recruiting with the violently changing world that was a big part of the so-called Summer of Love. "He had no interest in a war overseas," Guinn writes. "Anything that kept down blacks and women was just fine with him. And the only free speech he cared about was his own."

But he sensed the alienation, bewilderment and weakness that were part of hippie culture, and he knew just how to exploit them. Guinn describes Manson's keen instincts for singling out girls who were damaged (and receptive) but not broken (or too much trouble).

When the book follows Manson to Los Angeles and describes his followers' well-honed mooching methods, it is on much more familiar ground. But here again, context works to Guinn's advantage. He revisits the time when a star like Dennis Wilson, drummer of The Beach Boys, could be picked up hitchhiking, and when Wilson would have found Manson's criminal record a sign of outlaw cool. But there was nothing cool about Manson's pursuit of a mentor; he set his sights first on Wilson. Later, as he grew wilier about where power was in the music business, he targeted producer Terry Melcher. This book sees Manson's desire for musical stardom as the guiding force behind much of his brutality.

Guinn has a lot of evidence for that claim. His interviewees, including Patricia Krenwinkel and Leslie Van Houten, Manson Family members serving life sentences (as is their leader), help to recreate the elaborate lengths to which Manson would go to plug his musicianship - and the humiliation he could not easily hide when anyone who could make him famous wouldn't do it. The moment when Melcher paid the Family a visit and gave Manson US$50 - not for his music, but because the group's young children were being fed food from rubbish bins - was disguised as a triumph by Manson. But he knew better, and he wanted to get even.

This book overlaps somewhat with , the 1974 account of the Manson trial written by prosecutor Vincent Bugliosi. Guinn's much broader yet more streamlined book homes in on the tight suspense and drama of the trial, not to mention the bits of inadvertent comedy. Manson's hapless lawyer, Irving Kanarek ("Mr Manson is not all good"), managed to bore the jury into requesting NoDoz to ward off sleepiness and infuriate his client so much that Manson attacked him in the courtroom.

tells stories so well that it is sure to attract attention to Guinn's earlier writing. It makes sense that his past subjects include Bonnie and Clyde and the shootout at the OK Corral. It's more baffling that his primary subject until now has been Santa Claus. He has written Santa's autobiography, a North Pole cookbook, , and a book about Mrs Claus, too. To the great credit of this new book, is a lot more fathomable than the Guinn bibliography.