But please continue by reading more rigorous work on evolution, or you run the risk of being badly misinformed. I suggest, at a minimum, a decent textbook. Here I'd recommend Douglas Futuyma's Evolution.

Follow this up with some key works in the field, such as Gould's early critique of naive adaptationism, The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme.

Also consider different perspectives such as the those described in following books, which take, respectively, drift- and mutation-first approaches to evolution:

The Origins of Genome Architecture, M Lynch; and Mutation-Driven Evolution, M Nei.

Above all, know that evolution is far more complex, subtle (and interesting) than The Selfish Gene would have you believe.