KiCad 6 is a program for creating circuits and printed circuit boards as well as the Gerber files for further processing by board manufacturers. The program is open source and available for many platforms.
This small book is not intended to be a comprehensive documentation explaining all functions down to the smallest detail. It is simply meant to be an introduction for the practitioner who wants to design a circuit and use it to develop his PCB. And it's understandable and compact. Without going into the last possible option in the configuration, which you probably won't change after all.