A new Barack Obama biography has sparked a skirmish between Amazon and Barnes and Noble that opens a door into a war in which Amazon has been dubbed book publishing's Darth Vader. So reports Publishers Weekly in a column titled "The Audacity of Hype." The battle is over a sweetheart deal by a publisher that gave Amazon a two-week head start on the rest of the bookselling industry to promote Obama's Challenge: America's Economic Crisis and the Power of a Transformative Presidency.