Next year, I will give one of my SpaceX shares to every kid in America. This will be the first of many.

For two years, @WalterIsaacson lived in an Airstream next to Elon Musk while writing his biography. Isaacson didn't want a book built on a series of interviews. Instead, he got near-constant access to observe Musk firsthand. That's how he saw Musk's "demon mode" up close. Here's how he describes the mood swings: "He gets really dark and really difficult. He just goes silent." "There are people like Gwynne Shotwell and [Tesla design chief] Franz von Holzhausen who know how to push him out of demon mode. He also knows how to get himself together when he goes on stage." "It depends on what's crossing his mind at the moment. It's almost like a storm cloud coming in off the Gulf." "There'd be times I'd watch him go into demon mode. I'd be sitting at dinner at a restaurant in Austin and Grimes would be next to me, and she'd say, 'Oh, demon mode's about to come.'" "I'd watch people text Gwynne to come run into the conference room when he's about to kill Falcon Heavy or something." And he doesn't think Musk has gotten any less mercurial, either.