This book has been written by the processing fathers. That alone is a sign of quality. In addition, they are written completely understandable: It is suitable even for beginners without any basic knowledge of a programming language. It is didactically very well built with many examples that build on each other and little by little becoming more complex.
The most important basic concepts of programming such as loops, conditionals, functions, etc. are very well explained in the context of graphic representations here. (For example, a function is written to draw a predetermined pattern Next, a loop is used to repeat this grid-like pattern on the screen.).
So this book is not only a very good processing reference, but also a basic programming course for beginners.
For a reasonably experienced programmer, the book is indeed on a too low level. However, I myself use it anyway as a reference, since I find more comfortable doing a lookup in a book than on a website (the contents of which, however, now are much more recent).
The actuality is perhaps the biggest shortcoming of this book: From the Year 2010 Processing has evolved significantly: In the book, unfortunately, is still completely unmentioned the Android mode: So you can (also without much prior knowledge) create simple Android Apps on Processing.
What has me doing very enthusiastic: Virtually all examples in this book can be 1: 1 compile the Android mode and then run on a smartphone. Touching the screen will then replace only the click of a mouse. Kudos to the developers Processing for this backwards compatibility.
Therefore (and because there is no alternative to the book market) we use at Reutlingen University this textbook for school and student projects in the field of physical computing with Android smartphones.
The reason why I only 4 stars forgive the one hand, the above-mentioned lack of timeliness on the other hand also the black and white printing of the book now should for a book on graphics programming but the color does not fail as the printing costs ... ;-)