| A book by Steve Grand published in 2000. Grand is the main guy behind the computer game Creatures, and indeed the latter chapters of the book are dedicated to explaining the details of the Norns' code.
The first part of the book is a roller-coaster ride through an awful lot of things. The book won't tell you the details of how to write the code for artificial life programs, and is more of "a Zen-like guide to being a digital God". I came away from the book feeling that, given time, I could write a Creatures-like program.
Topics covered in the first part of the book include materialism, persistent phenomena, bottom-up design, computer simulation and autocatalytic networks. All of these things are geared towards getting you in the right mindset to understand what comes next: the details of the Creatures implementation.
A lot of things about the Norns are explained: the way their primitive brains work, the way their biochemistry works (yes, they have biochemistry! Why is explained in the first part of the book...) and how the reproduction/evolution works.
This book can be quite an eye-opener for someone stuck in a top-down mindset, and has something to offer to laymen and programmers alike. Programmers will find a rich source of ideas for their own projects, whereas the first part of the book has something to offer anyone with an interest in popular science or metaphysics. | 
