MARIA TAMBINE HEROINE of Andrew O'Hagan's new novel, is a personality with a personality disorder. A star at the age of thirteen after winning a TV talent show, the diminutive Scottish singer's showbiz career plunges her into a fight with anorexia nervosa that will last the rest of her life. For Maria Tanlbini, read Lena Zavaroni. This is not a biographical novel, as O'Hagan stresses in an author's note, and he does blend the facts with his own modifications and inventions. But the parallels are so close and so numerous there is no doubting that he found his inspiration in the tragic story of Zavaroni, who died in 1999, aged thirty-five, after two decades of eating disorders. He ends Maria's story earlier, enabling a more ambiguous closure. It begins, though, where Zavaroni's began, in Rothesay on the Isle of Bute.Born into an Italian immigrant family, Maria is still a schoolgirl when her remarkable voice makes her the star turn at local talent contests. A scout from Opportunity Knocks invites her to audition; she wins the show seven weeks in a row. Maria is signed up