The two main techniques that this book teaches are (1) behavior over time graphs and causal loops, both of which are the main tools employed in systems thinking. These are also the foundation of system dynamics of which systems thinking is a subset (system dynamics uses expanded techniques such as simulation models and analysis of alternatives).
What I like about this book is the clear explanation of the basics and the use of illustrations and learning activities. I also like the summaries of system archetypes and system thinking tools included in the appendices, which provide starting points for further study. It's not the best book for self-study because it is written more as a workbook than an introductory text. As such it is best used in an instructor-led course, or in conjunction with more in-depth books about system thinking (my favorite is Systems Thinking: Managing Chaos and Complexity by Jamshid Gharajedaghi).