Complex systems are all around us, and the topic is a hot area of study. But just what is a Complex System? They are not easy to define. Here, Ladyman and Wiesner discuss several aspects of Complex Systems, and tackle the definition problem. The issue is that there are several kinds of complex system, and there is not one set of features that is sufficient and necessary for all these kinds. What the authors do is discuss a collection of 10 features that cover these cases, and which features are applicable to which kinds of system.
The 10 features covered are: numerosity (many interacting components); disorder and diversity (no centralised control of heterogeneous components); feedback from iterated interactions; non-equilibrium (open to the environment); self-organisation emerging from interactions; non-linear dependence on driving forces; robustness to (certain) perturbations; nested structure and modularity including multiple scales; history and memory; adaptive behaviour.
This is a pragmatic approach to Complex Systems, putting structure on the domain without requiring overall uniformity. (The study of complex systems is complex!) It is a useful book that sits neatly between pop science introductory books, and more formal academic texts.