The irony of The Posthumous Memoirs lies almost entirely in the voice of Brás Cubas, who tells serious things in a light tone and lets the reader perceive what he himself does not say. The narrator defines it himself in the prologue to the reader: he wrote the work "with the pen of jest and the ink of melancholy". Laughter is the instrument; what it shows is sad.
Examples are everywhere. Of his first love, Brás sums up: "Marcela loved me for fifteen months and eleven contos de réis; nothing less." The phrase sounds like a declaration of love and is an expense account. After killing a black butterfly that came into his room, he comments: "See how good it is to be superior to butterflies!" And, when he speaks of the book itself, he blames the reader: "the greatest defect of this book is you, reader".
The irony also strikes Brás himself. He justifies himself with ingenious theories, such as the one that vice is often the manure of virtue, and the reader sees the interest behind the theory. That is why reading the book requires attention: almost nothing in it is said head-on, and the meaning lives in the gap between what Brás asserts and what the scene shows.