A great book to learn Processing

Recently I have been playing with the Arduino and learned a bit about Processing, a powerful programming opensource software that more and more artists are using for graphic and interactive art. I found this book: "Processing A Programming Handbook for Visual Designers and Artists" by Casey Reyes and Ben Fry. Really the best way yo learn about Processing, I don't know if you are able to learn such technical stuff through online onscreen documents, software Help files etc. but for me it is much easier to learn with a hard copy in hands. This one is especially well written, it starts slowly but gives you all the step by step details, exercises, concepts needed to really learn. I love it!