Dr. Dawkins wrote this book for the very specific purpose of providing copious examples to support evolutionary change over time through the mechanism of natural selection. In the preface (vii) he comments, ?this book is my personal summary of the evidence that the theory of evolution is actually a fact as incontrovertible a fact as any in science". Dawkins then proceeds to provide specific examples of evolution in each subsequent chapter. You may find it helpful to explain what Dawkins presented in each chapter to someone unfamiliar with the mechanism of natural selection. Doing this often helps solidify your understanding.