It's the old ,old regs-to-riches story familiar from countless soap operas,chick flicks and fairy tales.A struggling single mother manages to write a literary masterpiece in a café over coffee while her baby gently sleeps.The book goes unnoticed by perfidious publishers;rejection slips pour in.Just as she is about to admit defeat and return to her McJob,an astute agent spots the gleam of gold in his tottering slush pile.Leaping into action,he brokers a deal with a prestigious publishing house,and the book is duly issued without a sniff of pre-publicity or Sunday-supplement hoopla.But the public loves it,words get around,sales take off and it climbs to the top of the charts.The once impoverished author goes on to even greater success and lives happily ever after. Such a scenario,if pitched at a Hollywood producer,would doubtless be dismissed as too stereotyped,too schmaltzy,too Walt Disney for words.Yet that is exactly what happened to J.K.Rowling,the giga-selling author of the Harry Potter books.Or so the story goes.The real stoey of the Harry Potter brand-and it is a brand-is even more compelling than the fairy tale...