In the second part of Don Quixote, published in 1615, the characters have read the first part, published in 1605. They recognise Quixote from it. He arrives in places where his reputation is already in print, and people treat him as the man from the book.
The same second part also answers a rival. In 1614 an unauthorised sequel appeared under the name Avellaneda, and Cervantes's book responds to it.
This is where the old heroic form turns over. An epic hero's fame is sung after his deeds. Quixote's fame is sitting on the shelf before he arrives, and it is out of his control, because someone else is publishing a version of him. The knight who wanted to live inside a book finds that books now decide who he is, and one of them is a forgery.
I find that the most modern thing in the whole work. A man has to compete with his own reputation and with a counterfeit of it at the same time, and the only weapon Cervantes gives him is the authentic sequel.
Does the second part read better because of the rival sequel, or would Cervantes have written the self-aware version anyway?