I am a designer not a programmer and this book was extremely helpful for one of my projects.
For experienced programmers the examples maybe a little easy and the book may not be for them.
This book is a step by step introduction, with code explained line-by-line, on how to get started with producing data visualizations, using the Processing language. It starts of with the basics, then gradually becomes more complex as you get towards the end of the book. It was very easy to follow as a complete novice. Recommended!