Books about books, stories about stories

I realised that I enjoyed quite a lot of books about people entering or leaving books/fiction, and I wondered if there are more of these.

What I have read:
* The Neverending Story (boy gets trapped in a book)
* Inkheart (people are read out of or read into a book)
* Damascus Nights (story teller needs to be told stories to regain his voice)
* Thursday Next (detective in literature crazy parallel world enters famous novel to save the plot)
* Sofie's World (teenager discovers she's a fictional character)