As we discussed in our "Tone" section, Heinlein developed a special mix of languages (called a pidgin) for his narrator, Mannie. It's mostly English but with a blend of Russian, a touch of Australian, and a dash of folksie jibber-jabber—the language equivalent of pouring all of a fountain's soda flavors into one cup and daring your friend to drink the whole thing.
But if you're going to develop a whole new take on English, then you're writing style is going to have to match, too. Otherwise, it won't, you know, work.
Everything about the writing style in The Moon is a Harsh Mistress—from word choice to word omission to sentence structure—is dedicated to bringing Mannie's unique tone to life. Here's a sample for us to dissect:
Makes difference. My one grandfather was shipped up from Joburg for armed violence and no work permit, other got transported for subversive activity after Wet Firecracker War. Maternal grandmother claimed she came up in bride ship—but I've seen records; she was Peace Corps enrollee (involuntary), which means what you think: juvenile delinquency female type. (1.15)
Notice how the writing style often drops two important aspects of Standard English: subjects and articles. In this case, Mannie drops the subject of the first sentence entirely. Also, we're betting many of us would have written "in a bride ship" and "I've seen the records," including the articles without even thinking about it. But here, Mannie does not.
These mistakes are pretty typical of students who are learning English as a second language, since there are many languages that lack both. Japanese, for example, doesn't require you to state a subject explicitly if it is already known. (These are called null-subject languages, by the way). Likewise, the Korean and Russian languages lack definite and indefinite articles.
By adopting this writing style, the book provides Mannie a foreign vibe to native English speakers, and this is important because Mannie isn't a native English speaker. The writing style constantly reminds us that he isn't just a space-faring American—he's a native Loonie.
Sentence structures also give Mannie's voice this quality, adding a bit of everyman as well. In the example above, notice how the first sentence is very compact and short, but the next sentence is a long run-on. The third sentence is also long, though it feels like a bunch of short sentence quickly strung together. You'll also notice there aren't any large, academic sounding words—word of the day calendar fodder, such as proletariat, anarcho-communism, and onomatopoeia, are absent.
The result doesn't have a mastered, manicured quality. Rather, it reads like somebody who is simply entering the story in his journal or telling the story to you over some drinks. It gives Mannie an intelligent quality, but it's the everyman intelligence of someone who works a nine-to-five job and lacks a classical, upper-class education like the Professor.