There are three popular books that teach Processing to a reasonably advanced level: this one, Processing: A Programming Handbook for Visual Designers and Artists, by Reas and Fry, and Processing: Creative Coding and Computational Art, by Greenberg. They are all aimed at beginning programmers who are interested in graphics and computer art. They are all good books but Learning Processing is the best of the three. While they are all well written, the thing that sets Learning Processing apart is its overall organization. My impression is that Greenberg and Reas and Fry write like artists who can't wait to show you the next cool thing you can do; in so doing, they get ahead of the reader's understanding. Shiffman gets to the cool stuff, too - but every step is clearly spelled out and the skills and concepts build clearly and logically. I have all three books; this is the one I would choose if I could have only one but it's good to have all three because they each have different examples and a slightly different emphasis on advanced topics.