Jean Nepomucene Auguste Pichauld, Comte de Fortsas, was a man with a singular passion. He collected books of which only one copy was known to exist. If he ever discovered that one of the volumes in his library had a duplicate anywhere in the world, he would immediately dispose of it. So when he died on September 1, 1839 he possessed only fifty-two books, but each of them was absolutely unique.
The Comte de Fortsas: the literary collector who never existed
Jean Nepomucene Auguste Pichauld "collected books of which only one copy was known to exist." When he died on September 1, 1839, his entire collection went up for auction in Belgium... except, not really.