When I’m reviewing and editing nonfiction book manuscripts, I often find that similar thoughts and ideas reoccur throughout the text in ways that dilute their power as well as the author’s message.
For instance, a paragraph about the history of neuroscience is followed by one on art, and then more information about the history of neuroscience occurs many pages later and then again several chapters after that. Skilled writers are able to weave disparate information through their books in ways that serve the theme and provide cohesive narration. (Avant-garde writers, on the other hand, are a different story!) But most mainstream nonfiction writers, especially if they work without an outline, can lose track of their thoughts and confuse readers if they mix up things too much.
By putting similar information together, readers can follow a logical thought sequence and truly engage with the subject(s) in deeper ways. I call this keeping “same with same,” and it's relatively easy to accomplish.
Algorithms be damned. I have an old school suggestion for decoding your manuscript and locating the “sames": Read your draft all the way through using colored pens/pencils to mark the types of information as you go. Say, green for the history of neuroscience and red for art. By the time you’re done, you are likely to see a bold visual pattern that allows you to extract similar information and put it together in one place.
The work doesn’t stop there, however. Once you have the information in one place, it’s time to work on transitions, check for repetition, and see if you have gaps that need to be filled. Maybe you’ll find you have large subsets of similar information that can be placed in a few separate sections and still make sense. The point is that you won’t know until you do the color hunt, and then what you have to work with truly becomes clear.