This is a good book for those who are interested in learning about the development of scientific ideas over a period of millennia (Aristotle to Darwin). It is generally well-written, though a little sluggish in places, but worth the effort. I was particularly impressed in how challenging it was for each of the individuals described to make a living while theorizing, and in many cases to develop the courage to present their findings and hypotheses in the face of orthodox thinking. If you are looking for a book on the development of the theory of natural selection, though, it would be better to focus on Darwin and Wallace. And ... ignore the word "Secret" in the title; it is just a come-on, not to be taken seriously.