Today on this date Charles Darwin’s On The Origin of Species was published. If you haven’t, you should read it. I’m not sure if it’s the most influential book of the last few centuries, but it’s definitely up there.
That being said, sometimes people want to read something different that’s more recent. I would highly recommend Evolution: The First Four Billion Years. It’s an anthology of different thinkers from evolutionary biology, from paleontology, to genetics, and even to philosophy.