That is one of them! :) To be honest, I bought "Authority" but never got around to reading it - I am not an ebook author myself so just put it aside until one day I decide to write a book.
The other books of his that I found very useful (and inspirational) are "The App Design Handbook" and "Designing Web Applications". They are here: http://nathanbarry.com/books/
The other books of his that I found very useful (and inspirational) are "The App Design Handbook" and "Designing Web Applications". They are here: http://nathanbarry.com/books/