Don Quixote is famous for being the book in which the novel looks at itself in the mirror: a hero who draws his life from reading, a squire who contradicts him without ceasing to follow him, and an author who discusses the book itself within it. Carpeaux calls it "the novel of novels," because the contrast between appearances and reality is the very substance of the genre.
Success came early. Part One was published in Madrid between late 1604 and early 1605, in a hurried printing, and was an immediate popular success. The book records the effect: in Part Two, the bachelor tells the gentleman that more than twelve thousand copies of the history have been printed, in Portugal, Barcelona, and Valencia, and that there is talk it is being printed in Antwerp. In 1614 an author who signed himself Avellaneda published a false sequel, and its very existence shows the size of the success.
There is also what the book does with its own condition as a book. It places its characters inside a story they themselves have read, and debates within it what counts as truth: the canon of Toledo and the gentleman discuss what proves that a book is true, the bachelor points out the errors of Part One, and the narrator chooses, in Part Two, not to insert any more loose novellas. One reading presents Cervantes as the precursor of the novel.
Carpeaux adds two observations. The book will forever keep two classes of readers, children, who do not yet know life, and adults hardened by experience of it; and the book owes part of its universal importance to a misreading, as happens so often.