First and foremost, Stranger in a Strange Land is a coming-of-age story. Sure, Mike is already the age of an adult from the story's onset, but in terms of human development, he is definitely a child. He can't tie his shoes, he doesn't understand the purpose of or how to wear clothes, and he can't tell the difference between fiction and nonfiction literature. (And we're not talking about The Blair Witch Project, where they try to make it seem real. Obvious fiction stuff like Romeo and Juliet.)
As the story progresses, Mike develops as a person and grows from an innocent man-boy to a more aware man-man. Sure, we tend to think of coming-of-age stories as narratives that bring a person from one age to another—first I was a boy, then I was a man, and so on. But coming-of-age stories can be just as much about an inner growth journey as a physical one. Don't forget it.
Satire is also an important part of Stranger's genre genome, and it comes from the political, religious, and social commentary littered throughout the book. The novel could have used U.S. democracy as its political system, or it could have used Catholicism as the religion first visited by Mike—or any number of other political and religious combinations, for that matter.
Instead, the novel has the World Federation and Fosterism, two organizations that take concepts from real world systems and bloat them up to levels of humorous satire. Why? Here's our take. A satirical viewpoint ensures that the novel wouldn't feel like an attack on any specific institutions.
Doing it this way ensures that the reader (that's us) can consider the ideas presented without having to worry that their personal beliefs are being attacked. When a reader doesn't feel assaulted or insulted, they are much more likely to give a new idea a fair shake. Don't you think?
And finally, we've got some science fiction. Yeah, we hear you. "But isn't this book found in the science fiction section? How is that last in terms of importance?" To which we say it is and it isn't. (Ah, ambiguity.)
The purpose of the science fiction elements in Stranger is to provide a setting (see our "Setting" section for more details there). The setting gives the reader distance from the story, in theory to allow a reading that doesn't come with the emotional baggage a story set in contemporary society might have—just like with the satire.
So the science fiction does a lot of the heavy lifting so that the coming-of-age and satire elements can do their thing. But it isn't the focus of the story the way the other two are. It's more of a spice. An important spice, one you can't make the dish without, but a spice nonetheless.