I have tried doing the challenge three times, and never managed to turn it into a book. It's one of those things I think you have to "feel ready" in order to succeed at. For me, there has always been too many other things going on in the month of November for me to be able to focus very much... and I needed something more specific than just "I want to write a book" to start with... I want to start with a concrete idea and an outline to work from.