Stranger in a Strange Land depicts a future world that is oriented as much toward social and religious concerns as it is toward technical ones. In the novel Heinlein is frank about what he considers the pretentious, artificial, and shameful elements of modern society.

The various characters—both appealing and repugnant—represent a segment of society. The social institutions of the press, government, medicine, entertainment, religion, and the military all come under Heinlein's critical gaze. He uses the characters as examples of both the good and the bad aspects of each institution. Most are portrayed unfavorably, but a few emerge as responsible, honest examples of the best that humanity can produce.

The book presents such a variety of characters that most readers will find one representing their own point of view.

The novel then challenges the reader's assumptions about religion, love, and the nature of God against the experiences of two beings, one essentially alien, the other essentially human.

Valentine Michael Smith—the man from Mars—provides the alien viewpoint, while Jubal Harshaw, an almost impossibly knowledgeable and independent human, provides the human view. Their radically opposite opinions challenge the reader's beliefs about sexuality, religion, and society. Through the interplay of these differing views, the reader learns the value of the old and the new, experience and innocence.

As an alien, Valentine Smith brings a fresh perspective to age-old human questions: Why, when love is present in the world, is there also jealousy? Why, when humans seem to have an infinite capacity for creativity and justice, are they so often routine in their behavior and cruel in their treatment of others? If humanity is made in God's image, why cannot people treat one another as God wants? Smith's struggle with these questions produces new ideals for the reader to consider and shows how these ideals may be realized in the future—or present—world.