Awesome stuff. Can you comment of the actual production of the book, how it was written, marketed, etc? Seems like a nice content marketing case study.
Most of these started as one off blog posts. After a while we built up enough chapters that it didn't seem like it would be that farfetched to make a book. So we filled in the gaps on some chapters that were missing and turned it into a book.
The Zapier process is mostly outlined here: https://zapier.com/blog/how-to-publish-ebook/