Packing for Mars is a hilarious and informative book about the difficulties astronauts face in outer space. It covers most bodily functions, eating, and what happens to food (and bodily fluids) in zero gravity. However, it has very little to do with visiting Mars.
I admit that I found this book a bit slow at the beginning, but it perked up around the time she started talking about the sleep studies NASA is performing. I want $7000 to lie around in bed all day for 3 months! I even called up the number provided on the NASA website to volunteer, but the number didn't work. *sigh* Oh well, I really didn't want to ruin my bones. Having studied bones for my dissertation, I recognize the long-term effects of a study like that. I was also thrilled when Roach quoted my dissertation adviser on the effects of hibernation on bear bones. How funny!