The famous magician

"A certain writer ("past sixty, enjoying 'a certain renown'") strolls through the old book market in a Buenos Aires park: "My Sunday walk through the market, repeated over so many years, was part of my general fantasizing about books." It helps him "know what my as-yet unwritten books would be about." Unfortunately, he is currently suffering writer's block. Soon, however, that proves to be the least of our hero's problems. There in the market, he...