You either want a introductory book in evolutionary biology or a book that offers mathematica models of evolutionary processes.

In my first class of evolutionary biology I had this textbook: [Futuyama, Evolution][1] I think it gives a good start to the field and offers a good overview of the difference subfields.

If you think you already know enough about the concepts selection, genetic drift, molecular evolution, etc… and you want a book that provides mathematical formulations of evolution, then you might want to have a look into the field of population genetics. On [this post][2] you'll find some book-recommendations

If you are particularly interested into molecular evolution, I'd suggest: [Yang, Computational molecular evolution][3]

Maybe you are particularly interested into the statistical methodology used in DNA annotation or in phylogeny. Then…. I don't know! It's not quite my field!


  [1]: http://www.amazon.com/Evolution-Douglas-J-Futuyma/dp/0878931872
  [2]: http://biology.stackexchange.com/questions/16470/book-recommendation-on-population-evolutionary-genetics/16474#16474
  [3]: http://www.amazon.com/dp/0198567022/?tag=stackoverfl08-20