To Kill a Mockingbird by Harper Lee
Set in small-town Alabama in the 1930s, this American classic, celebrating its 50th anniversary this year, delves into the irrationality of prejudice, racism and class from the perspective of a young girl named Scout.
What makes this book so fantastic and such a timeless classic is the way Lee is able to address such difficult, complicated topics through the innocence of a child's perspective. For example, the scene when the mob comes to the jail in the middle of the night to lynch Tom Robinson, Scout saves the day but has no idea she's doing so. (One of my favorite scenes in the book.) She shows that by singling out someone in a mob and reminding them of their humanity and decency, he'll realize what he's doing is wrong and be more inclined to put a stop to it.
Lee gets the reader to hold a mirror up to herself and take a long hard look at her own prejudiced, judging self. If you haven't read this book, read it. If you have and it's been a while, read it again.