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No one’s writing style is wrong, everyone is different. There are really no two books that are written the exact same way. Many authors that write series books don’t always write the books the exact same.
Take the book series The Heroes of Olympus written by Rick Riordan. The books in this series are pretty much sequels to another series by the same author, Percy Jackson, and the Olympians, but they are very different. Heroes of Olympus is written from multiple perspectives while Percy Jackson and the Olympian series is written in first person and the entire time it’s the same character’s perspective. I, personally, enjoy the mixed perspectives of this story because it gives information about characters we wouldn’t get unless it is written this way.
Another instance is Suzanne Collins and her Hunger Games novel series. The three main books are written in the first person, and narrated by the same character the entire time, while the prequel book The Ballad of Songbirds and Snakes is written in the third person perspective.
Many book series are written in the same style for every book. Take the Dork Diaries series for instance. They are all written in first person and the same character the entire time, except for one called Dork Diaries: Tales from a Not-So-Dorky Drama Queen where it is written from the perspective of the bully character.
In conclusion, write how you want to. Take inspiration from other authors. Write mixed perspectives, single perspectives, or whatever you want! It’s your story, be creative.