Michael Ruse is an old hand in the philosophy of biology. He is eminently qualified to write this short book. An important attraction of it is the account of the history of the idea of natural selection. He argues that even though Darwin was clear about the importance of natural selection in accounting for evolution, many others, both in the 19th century and later, have construed its role differently.
Unfortunately, the book leans too heavily on explicating the history of ideas in general, and Darwin's account in particular. It spends less effort on giving an overall picture of the current state of knowledge. Also, the text should have been edited more thoroughly. I am also somewhat puzzled that some of the quotes Ruse uses do not really illustrate what he claims that they do. I do not think he fundamentally misrepresents the arguments of the authors he criticizes, it's just that the quotes he uses in some cases simply do not seem relevant to the argument he makes.
The discussion about the rival "root" (!) metaphors of mechanism and organicism is very clear, and is by itself as good reason to read the book.