The Selfish Gene is written by Richard Dawkins. It is one of the most recommended book written on subject of evolution. The book is very repetitive and thats makes it almost boring after sometime.
Dawkins approaches genetics in a language easy for most people to be able to understand without sacrificing too much of the science. The book is long and slow to read so will take you average 7 to 10 days to complete it.
Author emphasis a lot on Darwin theory of evolution. You can skip this book if you are not much in science fiction.