I have much more to come about the book on the main blog. But I wanted to send a Note now to make sure my readers know that this important work is ready for review.
I've read the introduction and Part 1, and I'm currently working my way through the rest. This is an excellent resource, I already know. Siobhan and her editor, Krista Stevens, have put in a tremendous amount of work and I already know I'm going to learn a ton about the project through this book.
In addition to the book itself, there are dozens of interesting interviews that were conducted by Siobhan, and archived on WordPress.org. There are more than six hours worth of interviews with Matt Mullenweg alone, and hundreds more with other early contributors, influencers, competitors and more.
The book is on Github already, and there are actually 17 contributors, though the writing is all Siobhan's.
If you want to read the book with the best experience, I'd wait until the ebook or print versions are ready. But if you — like me — can't wait to dig in, read it straight on Github. We are very lucky that someone as talented as Siobhan was given this responsibility; it's a special work for the WordPress community.