Murderer. Thief. Cannibal? Oh, the writer at work! Perhaps the way authors work was most famously described in two books by Janet Malcolm: ''The Journalist and the Murderer,'' in which she compares journalists to confidence men who betray their subjects without remorse, and ''The Silent Woman,'' in which she described biographers as ''professional burglars.''

You can see the writer at work, too, in Philip Roth's new novel, ''I Married a Communist,'' in which the main character's life is ruined when his ex-wife writes a tell-all book about him revealing that he is a Communist. In real life, two years ago, Mr. Roth's ex-wife Claire Bloom published a memoir accusing Mr. Roth of being a self-absorbed misogynist who forced her to make her own daughter move out of the house. To some readers of Mr. Roth, who has made a career of taking elements from his life for his fiction, his new novel about a neurotic, vengeful ex-wife, Eve Frame, is simply payback, an act of revenge for Ms. Bloom's invasion of his privacy.

Of course, great novelists from Flaubert to Joyce to Dreiser have used real people as the basis for their fictional characters at one time or another. And even when the central premise of a novel is pure fiction, elements of it are almost always drawn from authors' own experience -- the lineaments of a face, for instance, scraps of dialogue or newspaper reports. In his book ''Couples,'' John Updike gave one of his characters his first wife's feet, with toes that curled a particular way -- or so attested two writers, Bernard Malamud and Anne Bernays, who read the book and saw the former Mrs. Updike's feet.

''Writers have never made things up,'' the novelist David Leavitt said last week. ''All you have to do is read Proust to understand that.'' He was speaking at an Authors Guild symposium, ''Whose Life Is It, Anyway?,'' at the New York Society for Ethical Culture, and he should know. Five years ago, Mr. Leavitt got into hot water when he borrowed elements from the autobiography of the late poet Sir Stephen Spender's for his novel with a homosexual theme, ''While England Sleeps.'' After Mr. Spender threatened to sue because of copyright infringement, calling Mr. Leavitt's work ''pornographic,'' all copies of the novel had to be ground to pulp and Mr. Leavitt was forced to make revisions.