Man's Search for Meaning — Viktor Frankl (1946)

Viktor Frankl's account of his experiences in Auschwitz and the psychological theory he derived from them — logotherapy, the idea that humans can endure almost any how if they have a why — is one of the most powerful books ever written. Its central argument: that life has meaning even in the most terrible suffering, and that the last of human freedoms is the freedom to choose one's attitude to any given circumstances.