Help with copyright

Hello!

As you may know from my other posts, I am currently drafting a sci-fi series, and need some advice with copyright.

Whenever I watch movies that are adaptations of books or modeled after a book series, there is always a disclaimer that says something like “Based on the characters created by X Creative”. Because of this, I was wondering if I need to do something other than copyrighting the books within the series, and copyright the universe itself or the characters.

Does anyone have any thoughts about this? Have you completed a similar project?

Thanks!

@Josiah DeGraaf @Jonathan Shuerger @Sarah Lillian Friedl @Raymond Keith @Rachel Keith