One of the books I am reading about writing has stated an interesting benchmark in separating acts in a book; life the way it was before, the struggle, and the knockout. They suggest that in most movies, the separation of these acts usually comes at about the 30 min mark and 1.5hr mark. To be more specific, the 25% mark and 75% mark.
However, in writing a book, the writer suggests separating acts much sooner; at the 20% mark. So in a 20 chapter book, this would be at the end of chapter 4. I am kinda surprised by this. I would have thought it came sooner than that! The first paragraph and chapter of the book is meant to be as much of a hook as possible. I would think that an event (gateway) that acts as a point of no return would happen within the first couple of chapters. Waiting all the way to chapter 4 seems like it is taking awhile.
On the flip side of that, most books have different lead characters staggered throughout the book to help “string up” tension. So perhaps the second chapter of a particular chapter doesn’t happen until chapter 4 or chapter 5.
I find it amazing how much there is to learn about this writing craft!