Eli Bendersky's website John McWhorter is a professor of linguistics at Berkeley, and in this book he tries to shed some light on his fascinating occupation, presenting some aspects of linguistics in a popular and very readable style. The main focus of the book is the evolution of language, which the author tries to parallel to biological evolution. Much of the book discusses how languages change by combining, splitting, simplification and so on, with many examples taken from a multitude of languages - some well known, and some most people have never heard of.
A fascinating topic in linguistics is pidgin and creole languages. Since there are relatively many examples of the formation of such languages in recent history (mainly after the beginning of the European expansion in the 15th century), the topic has been studied well, and the author dedicates many pages to it.
Another thing I found really interesting is the discussion of the relative complexities of languages. Modern languages (especially the European ones) are much simpler than many primitive languages. As the author says (and his examples powerfully demonstrate), some of the world' languages are so complicated that one has to wonder how anyone is able to speak them. One example is a native-American language spoken in the north-western part of the U.S.A. that's so convoluted that children learn to fully speak correctly it with all the nuances only at the age of 10. There are actually reasons for this being so, and they are presented in the book.
There's a lot more to say about this book, but I'll stop here. It's definitely recommended.