“Those who have insinuated that Menard devoted his life to writing a contemporary Quixote besmirch his illustrious memory. Pierre did not want to compose another Quixote, which is surely easy enough — he wanted to compose the Quixote. Nor, surely, need one be obliged to note that his goal was never a mechanical transcription of the original; he had no intention of copying it. His admirable ambition was to produce a number of pages which coincided — word for word and line for line — with those of Miguel de Cervantes.”
Here’s a PDF of an English translation:
http://hispanlit.qwriting.qc.cuny.edu/files/2011/06/Borges-P...
The story has some really funny sections where Borges compares a passage by Cervantes with an (identical) passage by Menard, comparing their style and meaning (which are not the same!). It's just fantastic.