I'm really taken with the idea of a double narrative (Zampano and Johnny Truant, whom I might call JT because it amuses me) mostly because I think it's interesting how Johnny and Zampano work through this mystery with the monster/monstrous house/...whatever the hell it is.
Zampano intellectualizes the house: he reaches back into the past to ancient and canonical sources for clues on how to express and deal with this phenomenon, hence the bit about Minos' maze. If not that, he refers to other critical works somehow--if tenuously--related to the Navidson Record, though he tends to enjoy pointing out how they're wrong or misguided rather than actually thinking about how it might help. His parts are just as much a stream-of-consciousness narration as Johnny's are, they're just framed in a different way. Unlike Johnny though, Zampano seems not to be okay with suggesting things wholly on his own, and so he adds all the names in the side margins and other places to add a ridiculous sort of credibility to himself in a way that isn't actually...credible. We always mention how Johnny isn't a reliable narrator, but then neither is Zampano, at least not entirely. But I think Zampano's intellectualizing, at base, is something we can understand, as the highly-educated English majors we are. I feel like, faced with the absolute weirdness of the situation, we would also reach back into what we've learned, both the processes and the content, to find something familiar, hoping there would be a predecessor to help us understand.
Johnny, on the other hand, pulls from his own experiences, sexual and drug-induced in nature as they may be. His experiences as the house monster starts ripping his life apart parallel the growing knowledge of Navidson and the others listed in the Record, just as the form and the organization of the book itself degenerates. He is the layman to Zampano's educated man, and his experiences that he draws from are just as credibly incredible as Zampano's, and therefore have just as much merit. And let's face it, JT's sections are much more interesting and poetic to read than Zampano's seeming digressions. I feel like there's a reason for that.
This double narrative, on a larger scale, illustrates the very different ways that people can approach a particular problem/phenomenon. (I have a particular example to use here, but unfortunately it's further on than we've read). Not to go into the whole "is there really existence" debate, but it's entirely possible, as some of you have pointed out, that this whole thing is an imagined drug trip by Johnny Truant. But couldn't we say that about any odd experience we've had? Couldn't we also say that of literature, even that which we really like and in some way, believe that it's true? Reality and its relation to truth is a very postmodern problem that hasn't been solved, and it's definitely a central issue of this book. There's no way to tell what's real or true in House of Leaves, so the story comes down to what we believe as individual readers, not really being able to prove anything, just going from instinct and what we think might be true or real. And isn't that just like life?
You know, I think I like this book. :)