YA novel about characters in a fantasy novel who must fight to prevent the text of the novel itself from being corrupted

Question

I found a shabby copy of this book at the library in the early 2000s. The central conceit of the story was that the characters were characters in a stereotypical medieval fantasy book, and they experience people reading this book as being summoned to act out the events of the story.

• The protagonist is a princess in the book, and her "parents" are the king and queen in the book.
• The characters of the in-story book know when their book is being read and what format the book is in. I distinctly recall that a character complains about the book being read on electronic devices because they have to walk "down" as they perform the story.
• The conflict of the novel concerns some kind of corruption to the story; I don't really remember what this corruption was or why exactly it bothered the protagonist. However, the cause of the corruption is discovered by the end.
• The corrupting agent is marked by the color yellow. I don't remember if this was woven into earlier scenes or if it only comes up in the revelatory scene at the end. I recall that revelation as involving the realization that someone is wearing yellow socks.

The book itself was hardcover and I don't know if its condition was due to its popularity or its age. I somewhat recall there being a picture of a girl in a purple gown on the cover.

Answer 1

This might be Into the Labyrinth (2002) by Roderick Townley.

The Amazon summary of the book mentions the story being changed around:

What a relief when the old storybook is republished and the characters who live inside it suddenly discover they have Readers again - lots of Readers - especially when the book is loaded on to the Web. The endless reading exhausts the characters - but that's nothing to the problems they face as strange things start happening. Words get changed around, scenes disappear - and Sylvie and her friends must launch themselves into the labyrinth of cyberspace to confront a twenty-first century evil that threatens to destroy their world.

A quick mention on another site mentions the characters having to run down the screen:

[In Into the Labyrinth] the book is moved online, and they have to run down the screen. They get their dresses caught on the words, etc.

The book is the sequel to The Great Good Thing (2001) which doesn't seem to contain the bits about corruption or running down the page.