How Many People Can the Earth Support?
The best thing about this book is that it doesn't answer the question asked in its title. At least not directly. Joel Cohen understands that nobody really knows how many people can fit on our planet, thanks to constant technological advances in areas like crop yield. He is rightly skeptical of the Malthusian doomsayers who constantly predict catastrophe, but also shows that current rates of population growth cannot continue forever. A more extended discussion of politics might have helped--China's horrific one-child rule barely comes up--but for an honest treatment of human population dynamics, this is a very good source.