By John Hersey.
This should be required reading in US History. In fact, I'm considering e-mailing my AP US History teacher from high school, whom I haven't contacted in three or four years, and telling her so (or at least suggesting it.)
This short book, originally a (long) article in The New Yorker, details the experiences of 6 Hiroshimans who were lucky enough to survive the atomic bomb. It really speaks for itself.
See this paper for more information on the article's publication and the public reaction to it.