At the start of the book, we meet a guy named Alonso Quixano. Alonso is getting on in years and has enough money to keep him from ever having to work or clean his own house. So he spends most of his free time reading books, and there are no books that interest him more than books about medieval knights riding around on horses, and slaying dragons, and kissing the hands of fair maidens, and… well, you get the picture.
It turns out that Alonso likes his books a little too much, because one day, he decides to dress up in an old suit of armor and become a knight himself. He takes the name of Don Quixote and starts riding up and down the countryside looking for adventures. The only problem is that giants and dragons don't really exist. But fear not, because Don Quixote has such an active imagination that he believes everyday objects (like windmills, for example) are actually giant monsters.
Early in his journeys, Don Quixote gets himself a sidekick named Sancho Panza. Sancho doesn't actually believe all the crazy stuff Quixote is saying, but he knows that Quixote has a good bit of wealth and hopes to make some money by hanging out with the guy. As the story continues, though, Sancho actually finds himself starting to believe Don Quixote's craziness, and he even hopes that one day the Don will give him an island to rule over.
Once Don Quixote and Sancho set off together for adventures, there are really too many plotlines to talk about in this brief summary. For a more in-depth look at everything that happens in this book, go to our more detailed Chapter-by-Chapter summaries.
There are some friends of the Don's who want to cure his madness, and they devise all sorts of schemes to get him home to his bed. But they often underestimate the power of Don Quixote's imagination—not to mention the extent to which people will go crazy over a book. Just look at this Jane Austen fan club if you don't believe us.
At the end of the novel, Don Quixote realizes that he's nuts. But by that point, it's too late. Dude gets a terrible fever and dies in his bed. One of his only dying wishes is for everyone to know how stupid all those chivalry books actually are. It's kind of like someone today saying, "Hey, everyone who still watches superhero movies: grow up!" And that's more or less the reason Cervantes says he wrote this book.