I've noticed before, that the closer you get to the end of a book, the more the pieces fall into place. It's one of the ways you know you're finishing up. All the random elements you've been struggling with are in place, and now you can clean up around the edges, which strengthens the book.
In fact, I think maybe that last bit of tightening and focusing is what makes a book work.
I really felt that way with Led to the Slaughter: The Donner Party Werewolves. (Books of the Dead Press.) I finally got the book to where I didn't feel like I needed to add anything or subtract anything. It was complete.
I'm in that process with my current book, Faerylander, now.
That's why it is so important to have an editor, I think. An editor cleans up a lot of the crap so that you can see the story a little more clearly. Sometimes you can lop off scenes, or add that little bit more.
For instance, I have a description of the "Great Library" late in the book that isn't necessary. However my first description of the scene really wasn't adequate, so I take the latter scene and include it with the early scene and it works much better.
Another example: I've cut a chapter where the main characters are sitting in a diner talking things over. I have the Hero describing his Sidekick to the Sidekick's Object of Affection.
But I have an early chapter where the Object of Affection is asking the Hero about the Sidekick, so when I move the whole interaction here, it works.
These last minute adjustments are huge. And they can really only be done at the last minute, when you have the narrative firmly in place and can see it for what it is.
It's that last bit of effort that makes it a polished novel.
2 days ago