Need help finding books relevant to thesis!

Hi! I've never posted here but I remembered that this sub exists and can possibly help!
I'm currently doing my thesis for my masters in English focusing on readers as characters in novels, so I wanted to ask here for any suggestions you all might have related to books that feature the reader as a character in the narrative. My main text is Phong Nguyen's Roundabout, and the author ends up including the reader into the plot midway through the book, so I need some more examples of books where that happens. So if anyone has any recommendations for books in which the reader becomes a character, whether it's shown for a small amount of time or is a constant factor of the book, I'd be much obliged!