The Kindle version is just that. The Gumroad version gets you DRM-free PDF, ePub and Mobi versions all for one price.
Here's a video of the presentation I did that sparked off the idea for the book.
Code!
If you've purchased the book, you can get the code here:
If you didn't actually buy the book, and click that link, a random body part will fall off. Play it safe and buy the book.
And, enjoy some images made from the code in the book.