There are a number of books related to artificial life:

Free Books

Conway’s Game of Life: Mathematics and Construction by Nathanial Johnston and Dave Greene

Biological Bits by Alan Dorin

Rise of the Self-Replicators by Tim Taylor and Alan Dorin

Non-technical Books

Artificial Life: The Quest for a New Creation by Steven Levy

The philosophy of artificial life edited by Margaret A. Boden

Complexity: A Guided Tour by Melanie Mitchell

The Computational Beauty of Nature: Computer Explorations of Fractals, Chaos, Complex Systems, and Adaptation by Gary William Flake

Textbooks

Introduction to Artificial Life by Christoph Adami

Citations