1. THE HEART IS A LONELY HUNTER, by Carson McCullers
God, I love this book, even though it's highly depressing.  It's about a bunch of southern misfits who all find a best friend in a deaf mute man. 

2. WINESBURG, OHIO, by Sherwood Anderson
This one made me want to be a writer.  It's about a bunch grotesque, lonely people in a small town.  I can identify with this book.

3. THE STRANGER, by Albert Camus
I hope this one isn't too obvious.  The appeal for me is watching the lead character as he drifts through life not caring at all about anyone or anything.  I tried that for a month and it did not go so well.