I have no good Earth Science book suggestions. Because sex and biology is all the rage here.
So instead I'll recommend to you my Holy Trinity of science books...
Bryan Sykes - Seven Daughters of Eve About female ancestry and the genes that make tracing it possible.
Bryan Sykes - Adam's Curse A lot about the Y chromosome.
Olivia Judson - Dr. Tatiana's Sex Advice for all Creation A lot about what is sex, what is reproduction... for non-human, and a fair number of non-mammalian species.