What kind of titan of industry has a "giddy mode"? Or a "demon mode"? The two aspects of Musk’s personality are forces that drive his choices and behavior at work—and vectors Isaacson finds critical to understanding how Musk operates. From ripping out servers on Christmas Eve on a whim to buying Twitter against better wisdom, and reaming out staff members left right and center, we stare into the darker parts of Musk as chronicled by Isaacson.