Please add a book to a series

[Alessandra]

Hello,

Please add this book https://www.goodreads.com/book/show/5...

to this series:
https://www.goodreads.com/series/1404...

It's book #13.

Thank you.

[rivka, Former Moderator]

To be a series on Goodreads, books need to have more than a common theme -- like characters in common, an overarching storyline, a shared universe, etc. What makes this a series?