Nico made this note while listening to Karin Slaughter’s NPR interview.

People in story should matter to readers.

This note refers to which important idea found in the interview?

I'm one of those people who doesn't really think of thrillers in a conventional way

you have to make sure that the reader cares enough about these characters

"The Great Gatsby," where you had a lone gunman killing someone.

I'm thinking about the books I grew up with, even "Gone with the Wind,"

answer asap

You have to make sure that the reader cares enough about these characters.

Explanation:

In the NPR interview with Karin Slaughter, a famed thriller writer, she admitted

"What makes thrillers work is that they have to have a beginning, a middle, and an end. When you want a really good story and a compelling read, you have to focus equally on plot and character, and you have to make sure that the reader cares enough about these characters so that when bad things happen, they wanna read along."

So, when Nico noted his statement while listening to the interview of a famed thriller writer, he seems to be addressing the need for readers to have care for the characters in the stories they read. This note is a reference to the need for readers to care enough about the characters that they are reading in a book.

because each is self-sufficient.  

appeal to ethos is your answer.