The Kiwi's Egg: Charles Darwin and Natural Selection - Great Discoveries in Evolutionary Biology | Perfect for Science Enthusiasts, Students, and Book Clubs

David Quammen's book is excellent and he writes in a very relaxed way at the same time he discusses a great deal of information about Darwin and evolution by natural selection. Be careful, this is the UK edition of his book there is another with the same text but with a different title which is the US edition.