book, Fractal Cities: A Geometry of Form and Function is still the most comprehensive work on this subject. It is now available for free in pdf format at: http://www.fractalcities.org/ . Dr. Batty's excellent follow-up book Cities and Complexity: Understanding Cities with Cellular Automata, Agent-Based Models and Fractals is available through MIT Press and other sources. Hopefully, one day this book will also be available on-line
For other online papers concerning spatial analysis, many with an urban focus and several on aspects of fractal analysis, and agent based modeling, go to website of the Barlett School Centre for Spatial Analysis (CASA) of at the University College of London which Dr. Batty is associated at: http://www.bartlett.ucl.ac.uk/
I have recently co-edited a book along with two of my colleagues Ivani Vassoler-Froelich , and JesúsTreviño-Cantú, The Geography, Politics, and Architecture of Cities: Studies in the Creation and Complexification of Culture which includes two my articles, one on complexity theory and the other urban morphology. There are also other excellent articles pertaining to other aspects of urbanism. It is published by The Edwin Mellen Press is available for ordering directly through the publisher at http://www.mellenpress.com/mellenpress.cfm?bookid=8568&pc=9 . It is also available through Amazon and Barnes and Nobles by searching on the title. This represents a good book for not only as a reference for those teach or conduct research in urbanism, but also is one that it is enjoyable to read and is approachable even if you are not a urbanist.