I've got one main beef with the book, namely that Dawkins clearly states the purpose of the book in the Preface, and then does a poor job of following through. He starts out by mentioning a slew of his previous books before saying:
Looking back on those books, I realized that the evidence for evolution itself was nowhere explicitly set out, and that this was a serious gap that I needed to close.Sounds good, right? Books like The Blind Watchmaker and Climbing Mount Improbable are very good, but they explain the mechanisms of evolution and the conceptual issues of understanding how evolution works, such as seeing natural history through the lens of deep time and incremental change.
So what does Dawkins do, then? Well, he starts in on the conceptual problems of understanding evolution. Chapter 1 is devoted to the semantics of the word "theory" and how scientists use it as opposed to its everyday use. I thought, "Okay, fine...now in Chapter 2 he'll start hammering on about the evidence from the fossil record and molecular genetics". Nope.
Guess what he does in Chapter 2? He basically retreads the line of argumentation from On the Origin of Species. Namely, "Look at the powerful change and diversity brought about by artificial selection (i.e. selective breeding among domesticated plants and animals). Look at all the different breeds of dogs that all originated from a single species, the wolf." It's part of a strategy he calls "softening up" the reader to make the transition from buying into evolution by means of natural selection by realizing how powerful artificial selection is. It worked pretty well for Darwin, but he didn't have many alternative strategies to convince his readers. Genetics wasn't even been formalized or understood. There was very little of a fossil record, especially with regard to human ancestry.
But from a modern perspective, why start out by retreading a line of argumentation from 150 years ago, especially when you have giant mountains of hard evidence with which to convince the reader? It's very weak. If I were either a creationist or sitting on the fence, I would be utterly frustrated with the book by this point.
There's no need to "soften up" your readers. Hit them square between the damn eyes with the indisputable, incontrovertible evidence that all life on this planet shares a common ancestry. You can either fill in the conceptual arguments later, or better yet, refer them to your previous books.
Dawkins uses the analogy of the historical sciences, like evolution and geology, to the work of a detective coming on the scene of a crime. We have powerful evidence in the form of effects, from which we can solidly determine the causes, even though we weren't around when the actual event happened. We can determine very accurately how and how long it took the Grand Canyon to form based on an understanding of erosion and other physical processes, just as we can convict a murderer with a clear conscience based on overwhelming physical evidence (DNA at the scene, the bullet matching the suspect's gun, gunpowder patterns on the suspect's hands and arms, blood in their car and their house, and on and on). If the evidence is overwhelming, we have no problem confidently making the correct inference, even if we don't have an eyewitness or a confession.
The Dawkins needed to do, right out the gate, is present the damn evidence. Attempting to overcome the reader's conceptual hurdles to understanding the mechanisms of evolution makes Dawkins seem like he doesn't have a case and that he's stalling.
Chapter 1 needed to be a summary of the enormous amount of physical evidence we have from many branches of science that converge irrefutably on the fact that all life on this planet shares a common ancestry in a giant family tree that took billions of years to unfold. Talk about the overwhelming fossil evidence and the evidence from molecular genetics. And then work back from there. He probably gets to this later, but I'm afraid he probably loses a lot of the people he wants to convince very early on.