How the hell did Stranger in a Strange Land never get made into a movie or a miniseries? It sold extremely well. It had nerds and hippies clamoring for placement of the book in their hall of fame. It had sex, the future, space travel, aliens, religion and philosophical issues all wrapped into one package. Some of the futuristic predictions/references by Heinlein have sort of come true. It's timeless because he never puts a datestamp on anything. A producer could use the uncut edition and string out two full length movies of it or a nice HBO miniseries.
Heinlein was writing in the midst of space exploration, the changing of American mores and social norms, and the Cold War. When I read his novels, I find his type of science fiction to be more speculative fiction. Stranger in a Strange Land (SISL) has many elements that are purely fantasy, but when he describes say the development & history of a colony on the Moon in one novel, or how the government and a corporation would pick the first astronauts to Mars in SISL, it feels authentic. The intense advertising and consumer culture depicted in this book do not feel so far fetched when you look around today.
Central to the book is Heinlein's depcition of the 'alien' brought back from Mars. It is actually a man born on Mars from the first flight crew 20 years later. Born a human in an alien culture and then returned home to be an alien in 'his' society, Valentine Michael Smith is a rich character. The character grows, changes and develops in a well paced fashion. I would have loved to read more about Mike in his mature stage. Heinlein's aliens not only look different but have completely different ideas of time, space, value, etc. They are not as humanoid as most aliens are in sci fi novels. I praise that portrait of aliens as well as the portrait of aliens who do not do things we would deem good or acceptable. The aliens are not shown as superior or inferior to humans. In newer sci fi novels, it always seems like the authors are making some dumb ass multiculturalism point to show them either as superior to humans or inferior. In the instance where they are shown as inferior, it is usually because they exhibit some feature of a certain human group (Nzis) and are driven to eradicate/battle anyone they meet. I like to think that aliens might already know about us and are choosing to avoid us. If you have not read SISl, please check it out.