Whatever Enron has done to investors, not to mention its employees’ retirement plans, the ethically challenged energy-trading giant has been a boon to writers: Three have deals to probe the biggest corporate bankruptcy of all time. Joan O’Neil, a John Wiley & Sons publisher, signed last fall with journalist Loren Fox for ”Power Shock: The Rise and Fall of Enron.” More recently Doubleday won the auction for ”Power Failure,” paying, according to sources, $500,000 to ”Texas Monthly” scribe Mimi Swartz, who had been interviewing Enron whistle-blower Sherron Watkins before her letter to the CEO became public. ”We can’t give a definitive yes or no at the moment,” says Doubleday spokesperson Suzanne Herz, when asked if Watkins will continue to cooperate with Swartz. And PublicAffairs will publish ”Pipe Dreams,” by journalist Robert Bryce. ”He…has been following [the story] since well before anyone knew there was a story,” insists PublicAffairs editor Lisa Kaufman. Ladies and gents, start your engines.