In the annals of American literature, has there ever been a major writer more easily distracted than Norman Mailer? The author of such classic books as “The Naked and the Dead” and “The Executioner’s Song” had a penchant for tangents that took him, over the course of his 84 years, far afield of his chosen profession. “Mailer loved to drop everything, mobilize his energies, and launch in a new direction,” writes J. Michael Lennon in Norman Mailer: A Double Life, the first biography of the author to appear since his death in 2007.