Writing a series teaches consistency. Which is a good thing in writing. The author make less mistakes with the attributes and readers come to know the characters better. I”m mentioning it because I have read several stories where consistency didn’t transit in the story. The stories are often a great read as to why I enjoyed them but a more critical reader may have stopped reading.
Too many think consistency means boring and predictable. It doesn’t have to be. Working with one main character doesn’t have to be boring. You can grow your character. The character can live, grow, learn and change just like a real person.
It can add depths to the story if the character to interact with many more character than the single- plot where the character only interact with one or two others.
I realized adding more characters complicate the story but it can be done. How? Figure out the relation of the other characters to the main character before you insert them in the story. If they do not fit into the scene then toss them or use them in a standalone book if they are too interesting to be tossed.
No, stories don’t always follow the writer’s planned format. They often grow and take on a life of their own. That’s one of the beauties of writing. You never know where you may end up. 🙂