The number of people who finish a multi-chapter fan-fiction is, surprisingly, almost always 40-60% of the number who clicked on the first chapter, with the very best reaching 60%, and the misspelled, grammar-free, plot-free, alphabet-soup-vomit of ten-year-olds retaining about 40%.
That means that if you want to write a successful nonfiction book, you don’t have to optimize for getting a reader to finish the book but have to optimize for the reader telling other potential readers about the book so that they also start reading.
That means that if you want to write a successful nonfiction book, you don’t have to optimize for getting a reader to finish the book but have to optimize for the reader telling other potential readers about the book so that they also start reading.