The result was singing competition "X Factor," which had its debut in Britain in 2004 and in the U.S. last fall. Cowell also created "Britain's Got Talent" and executive produces its U.S. spinoff, "America's got Talent."
Cowell's response to the book, published in Britain on Friday, is so far unknown.
Publicist Max Clifford — who says Cowell pays him hundreds of thousands of dollars a year to keep stories out of the press — said he had advised Cowell not to speak to Bower, because it would undo years of carefully protected privacy.
"He knows it was a mistake," Clifford said.
"For Simon, who has protected his privacy and never, ever spoken about his relationships with anybody, to suddenly be quoted about this, that and the other is to me very damaging.
"Having created an image that's been hugely successful, to see him damage it like that is sad and disappointing," Clifford said.
Bower, though, thinks the book's portrait of Cowell is fairly positive.
While Bower has been openly hostile to some of his previous subjects — he called Gordon Brown a ruthless bully and Conrad Black a crook — he has a soft spot for Cowell.
"He's not a crook," Bower said. "So far he hasn't sued me. And it was good fun.
"He doesn't sit on his laurels. That's what's endearing about him. Although he is vain, he is a perfectionist and a professional — and he understands the business better than most."
Jill Lawless can be reached at: http://twitter.com/JillLawless
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