Processing Books

There are many good books on Processing and you can find a nice list of them on the Processing website here

My two recommendations to start with:

• Learning processing by Daniel Schiffmann (http://learningprocessing.com/)
• The Nature of Code by Daniel schiffmann (https://natureofcode.com/) <-- you can do this one online

And when you have read those then you are ready for:

• Generative Design (http://www.generative-gestaltung.de/)