When reading changed, so did writing.
Upper excerpt: "...what happened to him shall be told farther on. At the time when these things took place, as ye have already heard, there reigned in Great Britain a king named Falagriz, who died without an heir, leaving..." — Amadis of Gaul, Chapter 3.
Lower excerpt: "Idle reader: thou mayest believe me without any oath that I wish this book, as the child of my thoughts, were the most beautiful, charming, and prudent that could be imagined. But I have not..." — Don Quixote de la Mancha, Prologue.
In the introduction to the Spanish Royal Academy's 400th Anniversary edition of Don Quixote de la Mancha, Mario Vargas Llosa writes:
"Cervantes, in order to tell Quixote's deeds, revolutionized the narrative forms of his time and established the foundation on which the modern novel was born. [...] Perhaps the most innovative aspect of Quixote is the way in which Cervantes faced the problem of the narrator, the basic problem that must be resolved by anyone who wants to write a novel: who is going to tell the story?"
I think we should also ask: who is the story going to be told to, and how? The answer to that question helps explain the difference in narrative forms between Amadis and Quixote.
Amadis was written in Castilla-León the late Middle Ages by anonymous authors, and it was one of a number of novels of chivalry popular at that time. This was before the printing press, so books were copied by hand on parchment, which made them expensive and rare. Most people didn't read much, especially for pleasure. Instead, they listened to books at group readings for entertainment, including readings of novels of chivalry. Pero López de Ayala wrote at the end of the 14th century, "It also pleased me to hear these books many times," especially Amadis.
Often enough, these books were read during meals to audiences distracted by the soup or their dinner partners. A good story required plenty of action to capture and recapture the audience's attention, as well as a declamatory narrative style. You can see this in the text, which often addresses the listeners as "vos" in Castilian or "ye" in English, which is the plural form of "you."
You would have heard this book, not read it. Indeed, the style of the original Castilian makes Amadis is a stirring book to read aloud to an audience.
But around 1440, Gutenberg invented the printing press. By 1604, when Quixote was published, books had become more common and relatively inexpensive. Reading had become a private activity, and so, in the prologue, Cervantes addresses his readers with the second-person-singular familiar form of "you": "thou."
That reader would curl up in a sunny alcove with Quixote as if it were a close friend, and the words from the page would travel directly to his or her thoughts. Cervantes could count on attentive readers, and so the kind of story he could tell them could be different: intimate and nuanced.
Technology had revolutionized the act of reading. It had revolutionized "you." As a result, it had also revolutionized writing — that is, it had changed what authors could do. The printing press initiated a period of great and fruitful literary experimentation.
Will the Internet cause a similar revolutionary change? Will it change "you"? If so, writing will change again, and a new kind of novel will be born.