In this second Science of Discworld book, the authors explore what it means to be human and how humanity got to where it has. The wizards are concerned because the Elves have invaded Roundworld and started messing about with humanity. Their experience on Discworld is that Elves are no good. But it turns out that without them on Roundworld it is a different story. Without the Elves influence, humanity is dull apes living in a midden heap. With their influence, you get cities with heads on spikes and a form of theater. The wizards device a way to let the Elves influence humanity, but still get rid of them at the same time. It all hinges on William Shakespeare.

As with the first book, I found the wizard story a lot more fun than the science. The science chapters are interesting and informative though. They deal with what it means to be human, art, evolution, and so much more.