Cervantes writes bitterly against the author who published a book that purported to be a sequel to Don Quixote. Assuming an attitude of forgiveness, Cervantes writes that he has no desire to call the writer names and would rather "let his Folly be its own punishment." He expresses outrage, however, in some parables whose moral is that the writer should be cautious how he exercises his wit in the future.
The pirated version of Don Quixote, written by a man who called himself Alonso Fernandez de Avellaneda, would not excite much commentary if it did not include such a slanderous, spiteful preface. It was not unusual for an author to capitalize on a book's popularity by writing a sequel to it, but Avellaneda, in his preface, made fun of Cervantes' old age, his poverty, and his heroically maimed hand, and wrote that he wished to usurp the market of Don Quixote and ruin Cervantes' own chances at selling a true sequel.
Cervantes, in fact, allowed so much time to pass before he brought the second part of Don Quixote to his publisher that we may assume he might never have completed the work at all were it not for the spurious preface that stung him into activity.