Andres Valloud is the main author for this book, but several others contributed. It starts out with how hard programming is, especially developing consistent skill.
The second chapter deals with Smalltalk style, similar to Kent Becks famous Smalltalk Best Practices book.
Chapter three appears deceptively simple concerning refactoring boolean expressions, but the benefits add up quickly.
Apparently the Matrix class in Pharo 7 is being decommissioned, and the replacement is the parent class Array2D (which happens to be mentioned in this book). It doesn't have the same protocol (ie no #dimension: message), but can be used for implementing the Game of Life example.
From chapter 4, why did the original symbol version of VisualWorks 7 have issues with single char symbols? This chapter also introduces the credit card example.
Reflection tends to be used for writing code in the first person and creating an explicit representation of our concerns with our own lack of understanding