 Miller &amp; Page 2007 and Mitchell 2009 both contain a chapter devoted to CA: they are accessible introductions written by notable scholars. Ilachinski 2001 is an excellent starting point for the exploration of the CA literature: although not up-to-date on some technical points, the volume nicely introduces the field and covers its most important applications. Wolfram 2002 took some twenty-years and 1200 pages to be finished and is a passionate journey including bold speculations on the role of CA for understanding the universe and our place in it.