The House of the Scorpion is told in the third person, but the narrator must be Matt's imaginary best friend. How else can we explain that we hear what he hears, see what he sees, and know what he knows (for the most part)? We get the entire story (aside from the opening chapter) from his point of view.
At the beginning of Chapter 2, when a young Matt throws a temper tantrum to keep Celia from going to work, we know right off the bat whom we'll be closest to in the novel. The narrator says, "He shrieked at the top of his voice in a way he knew was irritating. Even keeping Celia home long enough to deliver a tongue-lashing was worth it. He couldn't bear being left alone for another day." (2.5) In this moment, we know exactly what Matt is feeling and thinking, and the only reason we know is because the narrator does, too. We are given VIP access to Matt's inner world. Lucky us.
Of course, getting the story largely from Matt's point of view means that we don't always know everything that is going on with other characters. Our cluelessness adds to our sense of mystery and suspense, but it also brings us closer to our hero. We learn things along with him. As Matt grows up and becomes more aware, we also learn more and become more aware of what exactly is going on in Opium.
The only times we know something Matt doesn't are when Farmer pulls a fast one on us, and uses something called dramatic irony. Bear with us for a moment while we toss a definition your way. Dramatic irony refers to a part of the novel when we, the audience, know something that a character, like Matt, does not. So when Matt is reading María's mother's book on Opium, we know more of what is going on than Matt, who finds the whole book weird. This doesn't happen much in the novel, but can you spot some other times where we're clued in and Matt's still in the dark?