In the non-fiction genre, a super fun and insightful book is Personality Plus by Florence Littaur. She has made a career out of public speaking and her basically Hypocratic approach to human interaction. It's a fun read and she includes her pretty famous personality test for you to take.

Many of my friends and I have stayed up all night doing this test on one another. It's a ton of fun to guess which "type" other people in your life are. I recommend it highly!