Chapters four and five are studies of two of the favourite "counter-examples" of creationists, the (repeated) evolution of flight and of the eye. Chapter six uses sea shells to illustrate the idea of a morphospace and touches — too briefly — on the question of how much variation exists. In chapter seven Dawkins actually accepts a form of hierarchy in evolution, in what he calls "kaleidoscopic embryology". (He seems to have been impelled to this by simulation experiments: someone give the man some ecological and biogeographical simulation software and he may accept the importance of other mechanisms in evolution that are not simply natural selection acting on genes!)
Chapter eight looks at "intentionality" in nature — what are animals and plants for? Here, as in chapter one, I don't feel Dawkins does justice to the philosophical issues involved, but perhaps countering simple popular misconceptions is more important. Chapter nine is a brief excursus on robots, van Neumann machines, nanotechnology, and related themes. The final chapter is a tour de force of natural history — a study of figs and their coevolution with fig wasps.
As an expositor of the basic ideas of evolution Dawkins is unmatched: Climbing Mount Improbable joins The Blind Watchmaker as one of the best popular introductions to the subject around. But it also contains some brilliant descriptive natural history, which will be appreciated by those to whom basic evolutionary theory is already familiar. (Several of the chapters could be read in isolation and would be good candidates for the Penguin 60s series.)
Climbing Mount Improbable contains an effective selection of black and white photographs, but Penguin slipped up badly with the text. The tiny font chosen is not appropriate for a work of popular science aimed at a broad audience. The quotations and footnotes, in particular, verge on the unreadable. (I only acquired my copy of Climbing Mount Improbable because my grandfather was unable to read it.)