"Autobiography," John Stuart Mill

John Stuart Mill was one of the original liberals, back when that word meant "person who believes in individual rights and free trade" and not "weakling who hates America."* I've had to read this book twice, and each time I dreaded it, and each time I ended up reading the whole thing with ease. Mill's reputation as being dry as dust helps, because when you get to the parts about his nervous breakdown and the paeans to his wife, you're pleasantly surprised.
* I personally don't believe that liberals are weaklings who hate America, but then again it's not as if you can find an American who will willingly call him- or herself liberal anymore, so debating whether liberals are nasty or not is a bit like debating what color of rock candy the Big Rock Candy Mountain is made out of.