The book is mostly about using Processing [1] to emulate natural things. For those so interested, Mr. Shiffman runs an online course doing similar things in p5.js [2] at the Kadenze online school[3].
This is great, didn't know about p5js. About 2 years ago I was searching for something similar to Processing in Python, but couldn't find anything that was suitable.
Perhaps someone knows some project that has filled that gap.
Daniel Shiffman is a very likable (and smart!) guy. I highly recommend his YouTube channel: The Coding Train. It's a lot of fun. https://www.youtube.com/user/shiffman
The Coding Train playlist on Youtube has a lot of great content. Not just Nature of Code, but full tutorials on making Minesweeper, Tetris and Snake clones, Git for Poets, Twitter Bots, etc. Best way to get a solid intro to creative coding and Processing / p5.js.
For me he is one of the best code teachers ever. Few people have the ability to turn a complex concept and explain it in a simple and fun way. Check his coding train channel.
It's a great book but his Learning Processing: A Beginners Guide to Programming Images, Animation, and Interaction (2nd Ed) is a better introductory book.
Processing is just a great tool (it's not important he picked it), like python to introduce people to programming. I love how he uses it to explain math concepts. I wouldn't recommend this as a starter book either though :)
[1] https://processing.org/
[2] https://p5js.org/
[3] https://www.kadenze.com/courses/the-nature-of-code/info