Real Bits - deeper understanding for those who want to know why ...

Dennett, Daniel. Darwin's Dangerous Idea: Evolution and the Meanings of Life. Simon and Schuster, 1995 (some say this is the best book ever written on evolution - and it all applies to software systems).

Langton, Christopher G. (Ed.) Artificial Life : An Overview (Complex Adaptive Systems). Bradford Books (MIT Press), 1997 (Langton is the guy who really launched artificial life as a discipline at the Sante Fe Institute).

Levy, Steven. Artificial Life: A Report from the Frontier Where Computers Meet Biology. Vintage Books, 1993.