Packing for Mars by Mary Roach

If you like non-fiction, this author is one of the best! The author is really funny as she discusses group dynamics, the Vomit Comet, the complexity of going to the bathroom in space and food. She actually goes and tries to experience the research and studies first hand. She makes science FUN! 

She also wrote STIFF about what happens to bodies after death, SPIRIT about the question of what happens to our "soul" and GULP about how our bodies process food.