I asked Pagebound for books with a book inside the book. The following list is made up out of those recommendations. In some of them the MC is writing or reading a book that you also get to read, in others it is short stories or oral histories. In all of them, you get more then just one story. I have not read all of these books. I am open to more recommendations.

NB The Book of Counted Sorrows by Dean Koontz is often referenced is his other works and only later was actually written.