I just finished The Poisoner's Handbook a couple of weeks ago. So good! If you haven't yet, I really recommend The Immortal Life of Henrietta Lacks by Rebecca Skloot. The Great Influenza by John Barry about the 1918 Spanish flu epidemic is another excellent book about the birth of scientific medicine, although it's long and kind of boring at times. I borrowed it from Manda so you can ask her if you don't want to get your own copy ;)

If you're interested about evolution, Why Evolution is True by Jerry Coyne and Evolution: the Triumph of an Idea are two of the best introductions to the theory, the evidence, and in the case of the latter, the history of the science from Darwin to today.

And I can't recommend enough anything by Carl Sagan. The man was a genius. Billions and Billions and Demon-Haunted World are two of my favorites.