How to Write a First Draft of a Book?

To me, a book is sort of like buid a house, right? So the idea that you would just build a really shiddy house,right? Ino waticurs. And so to me, i'm writing an introduction, and i'm knowing, ok,  this is like my first pass at the introduction,. But it gets me enough that i can get to the, let's say, the first chapter. That being said, i am going back and reviewing, and it's getting stronger each time i touch it.