Two features stand out most about this book, even moreso when taken together: its breadth, and its accessibility. Throughout the book, Dawkins relates a multitude of facts about various organisms, as well as scientific principles in general and discoveries in specific. All of this is done in layman's terms, making the book a very easy read. I read most of it either during fifteen-mintue breaks at work, or while undergoing plasmapheresis at the local plasma clinic. While not specifically saying so, The Ancestor's Tale touches on a wide variety of scientific disciplines, all of which lend something of value to the confirmation of the theory of evolution.
Biology, obviously, is steeped in evolutionary theory. Evolution is the basis of modern biology, after all, so it is unsurprising that there should be discussions of molecular genetics, taxonomy, ethology, and population genetics. But in discussing fossils, Dawkins also brings in bits from geology; bits of physics lend to his discussion of radiometric dating; chemistry is brought to bear in his explanation of RNA transcription and protein synthesis; statistical analysis plays a part in his relation of how molecular data is arranged and analyzed to determine degrees of relatedness between organisms and species; even general philosophy makes a few appearances, most notably (to me, anyway) in the Orangutan's tale, which includes a lesson in parsimony as applied to the attempt to determine how many trips were taken by ancestral apes between Africa and Asia.
I confess that I find it slightly jarring to use the term "gripping" to describe a popular science text, but this book is a real page-turner! Not only has The Ancestor's Tale provided a great deal of fuel for my 101 Interesting Things series, it's also enhanced my appreciation for the power of the scientific method and the wealth of opportunity available to us in the information age. This book contains more information in it than Aristotle probably had access to during his entire life. All in all, I think Dawkins has rightly earned his place as Professor for Public Understanding of Science with this book alone. If you ever have the time and the opportunity, I strongly urge you to work up the inclination to read this book.