It is an interesting essay. He starts the article with a story about a sheik who was trying to ban the teaching of the Copernican theory in Saudi Arabia in the 1960s. He used this episode as an example of the scientific meaning of a theory (hint: it isn't some wild speculation without evidence.) He then goes on to give descriptions of several compelling lines of evidence.
My favorite quote from the article is:
Seen in the light of evolution, biology is, perhaps, intellectually the most satisfying and inspiring science. Without that light it becomes a pile of sundry facts some of them interesting or curious but making no meaningful picture as a whole.
This matches my experience in biology. When I took biology in high school, my feeling was that it was just a bunch of facts that had to memorized. I learn best when I can see how the bits of knowledge are connected. I found the whole excerise to be quite boring. Once I understood evolution, the pieces started to fall together. If you want specific examples, I would highly recommend "Your Inner Fish" by Neil Shubin. He talks about the gill structures that are present in human embryos as well as why human males frequently suffer from hernias. (Have you ever wondered why you had to do the "cough test" at the doctor?) Now I find biology to be one of the most fascinating sciences and the majority of science book wish list is books about biology.