Stranger in a Strange Land chronicles the life and times of Valentine Michael Smith, a man born on the first manned mission to Mars. Unfortunately, everyone on the mission dies except for the wee-baby, Mike, and he is stranded on Mars to be raised by Martians. It's exactly like The Jungle Book, only it's set in space and with Martians instead of wolves. Okay, so maybe it's not exactly like The Jungle Book.
Twenty years later, a second ship called the Champion goes to Mars to discover not only the Martians but, to the crew's immense surprise, a fully grown Mike. The Martian Old Ones, heads of the Martian society, decide to send Mike to Earth. They want him to "grok" his home world—to intimately and completely understand it and its inhabitants.
On Earth, Mike is immediately transferred to Bethesda Hospital to sleep off a life-threatening case of G-fatigue when he meets Gillian "Jill" Boardman. At first, Jill decides she wants nothing to do with the Man from Mars. She changes her mind when her journalist friend, Ben Caxton, informs her that Mike is not a patient of the hospital so much as a political prisoner.
It seems Mike is the legal successor to a couple billion dollars worth of inheritance and might be, according to Earth law, the sole owner and sovereign of the planet Mars. Yes, the entire planet. Ben believes the politicians are trying to use Mike to further their own agenda, and he wants to bring the story to light. It's that age-old story of journalist meets dirty politician, journalist writes article—ah, you know how these things go.
Ben tries to spring Mike from his sterile prison only to find the Man from Mars has been replaced with a fake. After the failed attempt, Ben goes missing, and Jill worries for his safety. She finds the real Michael Smith is still in the hospital and breaks him out, in what is perhaps the lamest escape ever (no spoilers on this one, you'll have to check it out).
Two government agents track her down, but Mike uses his super Martian powers and sends both men into another dimension. Now a fugitive and a tad freaked out about the whole "agents winked from existence" thing, Jill decides to ask for the help of Jubal Harshaw, writer, gourmet, lawyer, philosopher, doctor, and crotchety old man extraordinaire. Jubal agrees, and Jill and Mike stay at his house.
During his stay, Mike begins to learn how to interact in human culture. You see, although his body may be that of a strapping 20-year-old human, his mind is completely Martian, so Mike has to learn everything from scratch: from tying his shoelaces to kissing girls to understanding human religion.
Eventually, the head of the World Federation, Secretary-General Joe Douglas, sends troops to capture Mike. But Jubal forces Douglas into negotiations with the Man from Mars instead and even has him release Ben Caxton, whom Douglas claims has been on a week-long bender in Mexico. During the conference, Jubal manages to trick, negotiate, and bribe his way to victory, arranging it so Mike keeps his inheritance and freedom and the Martians are recognized as the true proprietors of Mars.
Mike's next adventure takes him to a Fosterite tabernacle where he hopes to grok religion. In this future, The Fosterites are a religious movement that mix gambling, drinking, and sexuality with evangelicalism. Just imagine Las Vegas founded by a gang of evangelical preachers instead of the mob. Mike groks many aspects of the church he finds appealing but many he views as wrong.
Mike and Jill then travel the world together, so Mike can grok what it means to be human and Jill can learn the Martian language. He works a variety of jobs from carnival magician to casino game manager and meets Patricia "Patty" Paiwonski, a Fosterite completely covered from head to toe in tattoos. All the while, he reads about every subject in every library he comes across. Finally, Smith decides it's time he helped humanity and—what else?—he starts his own church.
Ben Caxton visits Mike's Church of All Worlds and discovers that Mike is teaching his disciples the Martian language, how to grok others, and the Martian understanding of God, which is translated to "Thou art God." Once the concepts are mastered, members of the church can access powers similar to Mike's. They are also nudists and freely share all commodities with each other, including sexual partners. The whole thing initially repulses Ben, but, after talking with Jubal, he decides to return and becomes one of Mike's disciples.
Later, Mike's church is burned to the ground, and Jubal rushes to help Mike one final time. He learns that Mike has been a spy for the Martian Old Ones, who may choose to destroy Earth in the future (scary, yes). Mike also confesses to Jubal that while he initially tried to reorganize human society to remove such things as hate and jealousy, maybe saving them from their fate, he feels that he has failed. Jubal convinces Mike that he has done something wonderful with his church, and Mike believes he groks in fullness now. An angry mob forms outside Mike's church, and when Mike attempts to preach to them, they kill him, turning him into the Earth's first Martian martyr.
The members of the Church of All Worlds go their separate ways, now millionaires thanks to Mike's shrewd business tactics. Jubal begins writing a story titled "A Martian Named Smith." Meanwhile, Mike goes to the afterlife to continue his work helping humanity.