This is an interesting application of the MVP (minimal viable product) and Agile approach.
I particularly like the idea of having alpha testers.
“Write a minimum viable book for alpha testers. I wrote each chapter for a group of 10 alpha testers who generously agreed to read early versions of the book and put it into practice. Because I was writing for them, I was more motivated to write regularly.”
Read blog post: Writer as Coder: The Iterative Way to Write a Book, by Leo Babauta