It is not clear from the introduction whether this book is about micro- or macro-economics. The list of chapters are definately macro- subjects but (and in common with so many others) the start is one of mixing these two subjects, admittingly after they are defined. Students of economics need to appreciate that macroeconomics is not simply scalled-up microeconomics, but that it requires a distant view taken of the system to cover it in a comprehensive way. The "trick" is to do this using the least amount of complication and detail. Very few writers have achieved this, and John Petroff is one who has not managed it. When properly done, the resulting model should be fully comprehensive and include all of the 19 possible different specific kinds of activities performed within our social system.
The model which I use and recommend may be found in Wikimedia, commons, macroeconomics, as: DiagFunMacroSyst.pdf . It also included in the Merlot Diagrams/figures/photographs
It will need to be enlarged in order to identify all 19 double flows of money, goods etc., as noted in the above comment.