Knopf will publish the fourth volume of Robert A. Caro's Lyndon Johnson biography next May. The book, titled The Passage of Power, continues the story told in Master of the Senate (2002), Means of Ascent (1990) and The Path to Power (1982). The books have been honored with a National Book Award, a Pulitzer Prize, and two awards from the National Book Critics Circle. Collectively, they've sold 1.5 million copies.