Cool!
Also, I posted some more feedback here...
I noticed some issues with Physics issues while working on the book. @jonathan might be interested in that info too.
No, I tried that with The Unofficial Stencyl Textbook. It seems to dilute the effect of sales. The idea is to have a big launch, lots of sales at once, so that someone at Apple notices. If Apple notices the book and then features it, that's good news for me – but also Tumult. People that might not have known about Hype could learn about it through iBooks and a different area of iTunes. It also helps with getting a beachhead in educational institutions. The book could be part of a syllabus for a course on Hype or Web Development / Design.
I'm about 20-25 percent complete. I just finished the Inspector panels, which was tedious. Once I get through the basics of animation, I can focus more on what can be built with Hype – and how to built it!