"Thinking in Systems: A Primer" by Donella H. Meadows 4/5
The book offers an introduction to system thinking and delivers it well. It starts with basic examples of systems and then goes further with more complicated ones, so it has everything that you would expect from a primer. Different kinds of systems are presented with all the features, behaviours and forces that drive them.
Seeing things from a different angle (using system thinker lenses) is a worthy tool in our mental toolbox. I appreciate the appendix with all the knowledge condensed into a few pages as it helps me get back to the topic. There should be a warning, like with medicine, that after reading you will start to see systems features wherever you look. No prescription needed.
Perceiving the world as a place of interconnected systems is a great extension of everyone's mental toolbox, and Donella Meadows, as an environmental scientist, cares about that. Nature is much more interconnected than we perceive.