Don Quixote was published in two parts—ten-year span—and written during a turbulent time in Europe. This was around the same time as Shakespeare was taking the stage and dazzling people with comedy and dramas of romance and intrigue.
For the world, it will always be known as the book about the guy “tilting at windmills,” unless they’ve read it, and even then, it becomes the delusional old man going through a midlife crisis and tilting at windmills with the fat guy beside him.
For a book that could be argued as the first European modern novel, it doesn’t get as much love as it should—unlike Tale of Genji, the Asian equivalent written in Japan.
How does a book credited by Dostoyevsky as “the saddest book ever written … the story of disillusionment” get credit as the first modern novel?
By introducing an unreliable narrator.
To get there, we have to understand that the books at the time were written for singular purposes. They were to tell history, teach morals, promote a single idea, and never strayed from the norms. Books were meant to show the royalty as fearless, the church as virtuous, and bad things happened to people who failed to be pure of thought and action.
What Don Quixote did was tell a story that poked holes in what was wrong with the beliefs at the time through parodies and satire as an old man with a portly squire went on an adventure and fought in honor of love (talk about a genre overload compared to the time). It pushed for open-mindedness, an enduring attitude, a search within oneself to be as valiant as the old knights, and to explore for more than the bottom line.
It achieved this through character interactions. As the cast of characters interacted, they changed. Their views on things shifted and were challenged by what they saw, who they talked to, and how they all interacted within the story and not just by the scene.
The most important aspect of their interactions came not in how they were dressed but in the spoken idioms/languages. Prior to this book, all characters spoke the same language—an aristocratic language of the elite if you will. Don Quixote turned this notion on its head with the mix of languages of high born (Don Quixote) and the low born (Sancho Panza), allowing them to be more than just their station in life but friends and teachers to each other about life experiences.
All of this lead to an unreliable narrator with a tale within a tale who challenged the various notions of the day and laid the path to modern novels with their mix of genres, multiple POVs, and so much more.