I decided to pick up and read John Maynard Smith's The Theory of Evolution (1995) to deepen my understanding of evultionary biology. My primary knowledge comes (mainly) from popular accounts of this field by the likes of Richard Dawkins and Carl Zimmer.
Even though I do not regret reading this book, I cannot really say I enjoyed the book, or that it was useful in understanding evolution better. Maynard Smith was a mathematician-turned-biologist and this is clear from his writing style. It is written in a rather dull and abstract way, which makes it hard to follow.
Especially when dealing with the genetic underpinnings of evolution, Maynard Smith makes it harder than necessary for the reader to understand the topic. I have read more modern texts - preferably with pictures and diagrams - that are able to explain the exact same topic in a much more practical and concise way. For example, describing the different effects of homo- and heterozygosity on phenotypes with words is a rather convulated way - compared to, say, a diagram.
Anyway, even though the book didn't really offer me any new insights in evolutionary biology, it was a good refresher. It helps to read different authors on the same topic; makes it easier to grasp the material (in my experience).
Evolution is a rather simple and beautiful idea: genes build bodies, via long chains of proteins building proteins. Genetic and environmental variations - during the development from fertilized egg to adult - lead to morphological and behavioural differences between individuals. These differences in traits result in differences in fit between organism and environment. These differences in fitness result in differences in reproductive success. Hence, the environment selects, via the built phenotypes, the genotypes that are - comparatively speaking - the best ones available. This leads, over geological time (measured in millions of years), to the accumulation of changes, resulting in different species. This, in a nutshell, is evolution.
Maynard Smith emphasizes the relative rol of natural selection in evolution. He explains how fitness can account for only a small percentage of the selection going on - most of it is contingent (for example unfortunate individuals dying having nothing to do with any fit whatsoever). He also explains how evolution is continuously going on: an ever-changing environment leads to an ever-changing fit between individual and environment. Hence, evolution is undpredictable and can only be distilled with hindsight. A last important point is the infamous bottleneck in evolution. All (higher) organisms have to go through an emryonic and youthful stage. This means that genetic changes have an effect on the development of organisms, and hence are 'constrained' by the body plan that they alter. Most changes in the DNA are developmentally neutral/non-existent; most changes that aren't developmentally neutral are developmentally disastrous, leading to the (early) death of the organism. Natural selection has to 'work' with the minimum of variation that is available. This is an important point that Maynard Smith works out with great detail and in all its complexities (for example, the existence of a minimum of variation in populations).
So, can I recommend this book? Not really, rather pick up a contemporary biology textbook and study the topics. On some points Maynard Smith's book is outdated, as well. In the last chapter he tries to hypothesize about human ancestry - a domain which has been flooded with recent discoveries, culminating in a much more complete (and certain) history of mankind. The same thing concerning genetics; modern day genetics has progressed since the time Maynard Smith wrote this book, so it would (probably) be better to pick up a more recent book.