Certain works of art have an occult way of finding us when we are most in need of them, of their example and wisdom and wit. One night recently I was considering ways to wiggle out of having to write a memoir, which I had insensibly signed a contract to do, and was moving alps of books from one corner of my library to another. There, atop a shelf, reemerged a gift from a friend in the South: not a book, but a DVD collection of the films of Ross McElwee, the North Carolina documentarian whose far-famed Sherman’s March is a charismatic masterwork of autobiographical filmmaking.