I have long been of the opinion that historians and biographers need to write with a great deal more humility. We're always searching for the 'key' to understanding a person, or for the right moment or metaphor through which to interpret everything else about someone. The truth is that people are complicated, and according to C.S. Lewis, who was able to see people write about him in his own life time, most people who try and guess about another person's motives for what they do are wrong the vast majority of the time.
Mark Twain apparently valued his celebrity status during his life, and for whatever reason, decided to make sure his autobiography would not be published until 100 years after his death. Well, volume one is on the way soon. Sorry, everyone who has ever written a Twain biography, your work is about to be completely outdated. I bet it is all going to be a fascinating read. You have to admit, there are very few people who have the influence in this world to create gossip about themselves over 100 years after they are dead.