SOLVED. Book Characters Run Between Pages. [s]

[Jacob]

This is a book that my mom and sister read several years ago (around 2008). It was about the characters in a book, and how they had to run between the pages to arrive at the page the reader was reading. I think it talked about what they did when the person wasn't reading, and focused on them learning how to communicate with the reader (that seemed to be the problem/crux of the story).
It's not Inkheart etc. or In Between the Lines (Jodi Picoult)
Any help remembering the title would be appreciated.

[Rosa]

The Great Good Thing?

[Jacob]

Yup, that was it, thank you!

[Rosa]

Good, you're welcome.

Note to mods: maybe in the Group Rules, you should add a note about first making sure your forgotten book is not The Great Good Thing or The Thief of Always.