Reddit mentions of The Posthumous Memoirs of Brás Cubas (Library of Latin America)

As a Brazilian, I have some recommendations:

• Machado de Assis: there's a brief bio and some of his books here, but my favorite is this one. This one was written at the end of 19th century, and Portuguese was never so beautiful.
  
  
• Jorge Amado: I think he is the writer that captured many aspects of Brazilian culture such as religion, costumes, sex, humor, violence. Many of his books were adapted to movies or soap operas.
  
  
• Nelson Rodrigues: he was most famous as a play writer but his short stories are amazing. I think he is just like a Brazilian Bukowski. His stories are full of adulterers, perversions, humor and fast dialogues.
  
  I shouldn't be promoting those damn Argentinians ;), but this guy is really good:
  
  
• Jorge Luis Borges

The Posthumous Memoirs of Bras Cubas, by Joaquim Maria Machado de Assis

He beat them all on postmodernism by half a century or better, and he did it with style. Seriously, with a line up like that, I can guarantee beyond the shadow of a doubt that you will love this book.