Harper Lee's To Kill a Mockingbird was voted the book to read before you die by British Librarians, beating the Bible to top place. I don't quite agree with that order, but it should definitely be in the top three. It is such a beautiful gem of a book.
It deals with such deep issues—racial inequality, class, rape, justice—but from the view-point of a 10 year old child (well, the narrative voice is clever and complicated). Harper Lee does this to inject innocence and humour into otherwise appalling situations.
Interestingly, To Kill a Mockingbird has seen its fair share of controversy. When it began to be taught in schools, parents asked for it to banned, because most were apparently horrified by the idea that a white girl could be attracted to a black man. However, the book has later been said not to be as critical of racism as it should be, resulting in a further call for it to be banned from teaching syllabuses. Admittedly, the word 'Nigger' is used 48 times in the book, but you always get the feeling it is not used as a derogatory term. Sometimes the best way to remove a defamatory word's power is to claim it for a use that is not; just as the LGBT movement has for the word queer, and some feminists have tried for the 'C' word. Also, the book leaves no doubt as to who you were meant to be supporting.
One more note: Pullman, this is an example of what it is to do accents properly.
So, read it before you die. If you don't do it for me, do it for the librarians.