There is no one way to write a book. Everyone has their own way of thinking, and of organizing those thoughts.
When I did technical writing, the best way to do that was to pre-organize an article (or a book) via outlines, and then write the text. In those cases, I started by KNOWING what I wanted to say before I wrote the article or book.
Fiction is very different. It's more creative. For ME, I find that the story evolves as I tell it. I do not "pre-organize" the entire book. I write. As I write, characters develop, and problems unfold. These are the bases for what I write next.
Does EVERYONE write fiction this way? I don't know, but my hunch is that most people do. It might be that there are some masters of the craft that can outline their entire book before writing it.