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
Mitchell, M. (2011). Complexity: a guided tour (1. iss. as an paperback). Oxford University Press.
Flake, G. W. (2008). The computational beauty of nature: computer explorations of fractals, chaos, complex systems, and adaptation (9. print). The MIT Press.
Adami, C. (1998). Introduction to artificial life. Springer.
Boden, M. A. (Ed.). (1996). The philosophy of artificial life. Oxford University Press.
Levy, S. (1992). Artificial life: the quest for a new creation (1st ed). Pantheon Books.