Well now that we know what to fill a book with, we need to look at how it is presented:- the structure.
Structure is the way you present the story, it has stuff like acts and story divisions. It asks ‘how many acts should there be in a story?’
To answer that, we must answer the question ‘what is an act?’, simply put, it is a self contained chunk of story that has its own unique feel. Most movies and for that part books nowadays are divided into three acts. Some authors quite literally divide their books into three parts or more.
The three act is the most common way of dividing a story. Here is how it is divided:-
Most of the times, the first act is something that introduces the world and characters to the readers, it lays out the situation and introduces the readers to the rules. It can be an exhilarating part of the story in which the protagonist alongside the readers is thrown into a new situation that they have to make sense of or it can be a quiet beginning where the world and the character are introduced slowly alongside the story’s conflict.
The second act then shows the actual adventure, the characters explore the conflict. This is where the major portion of the story goes by. It can either be a slow middle after the explosive opening, where the character learns new techniques, gets used the change and forms new relationship or after a slow opening, this is where the protagonist is thrown into a turmoil and the majority of the conflict occurs.
While the third act is where the final confrontation or the climax of the story occurs, when the protagonist faces off against the antagonist or the the protagonist has to go through one last challenge to get their prize and then after that the conflict is solved and everything is happy forever after.
This structure is why trilogies are so popular, each book could represent a single act even though each may have a three act structure of its own.
Aside from the three act structure, we also have the five act structure that William Shakespere popularized. It allows the story to be developed in a much more extensive manner. We can have a different act for setting the scene, rising tensions, the push over the edge, climax and then the aftermath. In fact some experts believe that we write most of our stories in five act structures, we just force them into the molds of three act structure forcefully.
There is even a seven act structure, you can see how the harry potter series developed for an example of it.
Then there is the six act structure where we take a three act structure and divide each act into two.
What type of structure you choose or whether you choose one at all is up to you. There are people who argue for all types of structure, each story has a different type of structure that may suit it, so it would be good if you find the kind of structure that suits your story by experimenting.