Nathan is a good friend of mine (we used to work together) and he does have other books: http://nathanbarry.com/books/

I believe the impetus was more that self publishing is not that hard (although, writing is hard, just the other parts are easy) and you can make some money at it.

I second that. I recently had the chance to participate in an online conference with Nathan. He came across as real and friendly. He took the time to understand every question from the audience and gave thoughtful answers. I don't believe in get-rich-quick scheme either. Writing a book definitely takes a lot of time and effort. My wife recently wrote a 10-page tutorial on a single topic about Revit. It took her like 2 weeks with all the research, writing, and editing. If you are looking to make easy money quickly, this book is not for you. No book will ever be right for you. But if you are willing to put forth the effort, I think at least some people who can learn from you can benefit and appreciate.