To Kill a Mockingbird
I read this book in school and had forgotten all but the basic story line (somehow I forgot all about Dill, and most of the townsfolk, and their Aunt). I was listening to the section following the trial when Atticus is talking to Jem and getting frustrated in how little somethings seem to have changed.
I could go all into the things I'm sure I wrote English papers on but I still find this to be an important read, and I'm glad that I could get reacquainted with it.