Fantastic book. chapter 13 was probably my favorite chapter. Thats where everything comes to a head and he brings up the similarities between different species as well as vestigial organs and how it could have served previous generations but be rendered useless or redundant now. It was impressive that he noticed and brought up several things that would later be fully explained by science. One such thing was linked genes. When talking about pigeons he mentioned that beak size and foot size would always be correlated. He admits hes not sure why but in all cases with pigeon breeding if you have a small beak you have tiny feet. As an interesting note: he never brings up the finches. Ever. He hardly ever mentions the Galapagos. Mostly that he visited it and it had a small highly specialized group of species.For the most part he talks about fancy pigeons. So if you want an easier time reading the book go look up fancy pigeons, look at all the different breeds of domestic pigeons, memorize them, then read the book. Trust me he brings them up a lot.