Books
Processing: A Programming Handbook for Visual Designers and Artists by Casey Reas and Ben Fry
Learning Processing: A Beginner's Guide to Programming Images, Animation, and Interaction (Morgan Kaufmann Series in Computer Graphics) by Daniel Shiffman
Processing for Visual Artists: How to Create Expressive Images and Interactive Art by Andrew Glassner
Processing: Creative Coding and Computational Art (Foundation) by Ira Greenberg
Generative Art by Matt Pearson