A First-Rate Madness: Uncovering the Links Between Leadership and Mental Illness, by Nassir Ghaemi. It speculates that, in troubled times, what you need from a leader is the unconventional thinking that comes from certain specific kinds of mental illness. So far, it has presented a fairly convincing case that General William Tecumseh Sherman was bipolar and that it's part of why he was so skilled during the Civil War. He doesn't focus on Robert E. Lee, but he suggests that there might be some issues there, too, which I think might explain Pickett's Charge better than any other attempt I've heard.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"