In this context, the title of the book could be misleading to someone completely new to the subject. However, Adami makes it clear in the introductory chapter that he will be pursuing his own line of enquiry in subsequent chapters and not providing an overview - pointing readers to Langton's book for that. The chapter continues with a brief exposition of Turing and von Neumann Automata. Adami points out that, although having certain life-like properties, virus codes are consciously constructed by programmers and are also brittle to mutation. Tierra works because the instruction set used by the programs is less brittle to mutation.
Mutation thus has a good chance of producing new replicating programs.
Adami selects the Tierra framework as a paradigm from which to construct computational experiments for the rest of the book. An overview of this system is then provided. This chapter is a textbook introduction to information theory but with an eye to its application to living systems - specifically genetic codes. The next chapter is a primer in statistical mechanics and thermodynamics. From this he argues that any theory of complexity must be based in statistical physics - predicting aggregate behaviours from microscopic interactions.