Fascinating overview, and high quality science writing, with good approachable summaries of current research. Zimmer makes excellent points about how the notion of parasite is being redefined to remove the 'yuk' factor, so that humans can be seen as a kind of parasite—even possibly learning something about the stewardship of the Earth from our fellow parasites. There's a bonus NZ mention of Curtis Lively's work on the evolution of sex in indigenous aquatic snails.