When you are reading a book it’s easy to feel the continuity and arch of the story, especially when it flows right along. But what about a writer’s mistakes, the wrong turns taken? Hopefully you don’t see the evidence. You don’t see them because, if the writer and editor have done their jobs, they are no longer in the book. Those false steps were erased. Who was it that said the writer’s tool—a pencil—has two equal ends—the leaded end and the eraser end?

Now I’ve been working on a book for a good number of months. Generally speaking it was going well. Then, perhaps a month and a half ago I decided on a big change, and worked accordingly, so that that change manifested itself everywhere. But after all that was done, I decided I had made a poor decision. That meant going back and eradicating all traces of that choice. It was as if, having painted the house a certain color, cellar to roof, I realized my selection was poor. Even before I repainted, I had to remove the old color—(hopefully) all of it. 

So on one level I lost a month’s worth of forward progress. Yet I have learned, that even this kind of work—and some of it is drudge work—brings the writer into a better understanding of the work in hand. 

There is a perfect art term for this: pentimento. “A sign or trace of an alteration in a literary or artistic work; (spec. in Painting) a visible trace of a mistake or an earlier composition seen through later layers of paint on a canvas.” OED

Every book has such layers.