As a boy I read voraciously. I remember my mother organizing weekly trips to the town library, where I would load up on books, and I quickly became focused on Science Fiction, along with the usual stuff kids read, like the Hardy Boys, Tom Swift, and the Walter Farley horse books. But the idea of going into space grabbed me very early. And one of the first authors I read was Heinlein. He had taken a leave from publishing during World War II, when he was doing research at the Philadelphia Navy Yard. But when the war was over, he set out to move beyond the “pulps” and expand the market for his stories. And one big market for him was what were called “juveniles” at the time, and would today be called “Young Adult”. I was reading adult fiction by the time I was 11 or 12, but before that (and even after that, in fact) I read these Heinlein novels with great relish.

Heinlein’s target audience for these novels was teenage boys. He did a few stories aimed at girls, but mostly he wrote for boys. And these were mostly “coming of age” stories where the teenage protagonist has adventures, and as a result grows and develops. They are very loosely related via some internal references, but should really be thought of as stand-alone stories. They also in some cases have references to his other stories, including the Future history stories. He wrote 13 of these novels, one per year, from 1947 to 1959. The series was published by Scribners until the last one was rejected by them. Heinlein then published it with a different publisher, and stopped writing these novels altogether in favor of more adult fiction. The novels roughly form a progression telling the story of space exploration. It starts with a trip to the Moon, then Venus, Mars, Jupiter’s moon, and so on until we reach the Lesser Magellanic Cloud.

• Rocket Ship Galileo (1947) – While readable, this initial effort was not up to Heinlein’s later standards. The plot concerns three teenagers who assist an uncle to build a rocket ship and go to the Moon. When they get there they discover Nazis have already arrived. The Nazis try to kill the group, but they succeed in turning the tables, stealing the Nazi ship, and returning to Earth as heroes. This novel became the basis (loosely) for the movie Destination Moon (1950), and I personally would consider the movie to be superior to the novel. It is also worth noting that the theory brought up in Blowups Happen reappears in this novel. They find evidence of an ancient Lunar civilization that was destroyed, and theorize that the craters on the moon were caused by the explosion of nuclear reactors that caused the extinction of the civilization.
• Space Cadet (1948) – This was in part the inspiration for the Tom Corbett franchise, which licensed the name Space Cadet from Heinlein. It is about a young man who is accepted to the Academy for the Space Patrol. It follows him through his education in the Academy, and then into his first mission after graduating. This holds up better than the previous novel. And it is tied back to the story The Long Watch from the Future History. Part of the story takes place on an inhabited Venus that is cloudy and swampy.
• Red Planet (1949) – This is set on Mars, as it is also portrayed in Stranger In A Strange Land (1961). Mars is inhabited by native Martians, but also by human colonists. It has the canals, and with seasonal changes the colonists migrate from north to south and back. A pair of teenage boys get caught up in a revolution when the evil corporation that controls the colony pushes the colonists too far. In the end you wish there really were canals and Martians.
• Farmer In The Sky (1950) – This is one of the best, as seen by the Retro Hugo this novel won in 2000. Jupiter’s moon Ganymede is being terraformed because Earth is overcrowded and food is rationed. A teenage boy and his family emigrate to Ganymede and try to make a life there, which they eventually succeed in doing. The Green Hills of Earth is mentioned here, tying this into the future History. There are frequent references to the Boy Scouts, due to the fact that the story ran as a serial in Boy’s Life magazine.
• Between Planets (1951) – A teenage boy is caught up in interplanetary intrigue. Venus and Mars have colonies, but Earth is trying to control them too much. So revolution is on the menu. This is clearly patterned in the colonial wars of the 18th and 19th centuries, such as the American Revolution against England. By this point the so-called “Juveniles” are really having more adult content, and reviewers re starting to rate them in comparison with adult science fiction. This novel was also first serialized in Boy’s Life magazine.
• The Rolling Stones (1952) – Here we have teenage twin boys, Castor and Pollux, as the protagonists. They and their family live on the Moon, but decide to travel, so this novel is a kind of travelogue as they go to Mars, then to the Asteroid belt. The grandmother, Hazel Stone, appears in Heinlein’s later works as well. One interesting episode in this story involves “martian flat cats”, which are furry, lovable, and reproduce like mad with the right conditions. If this sound like Star Trek’s Tribbles, that is also what the Star Trek producers thought, so they got permission from Heinlein to use the idea.
• Starman Jones (1953) – We are now further into the future, and the human race is exploring the stars. Unfortunately, very restrictive guilds closely control who can participate in this. A teenage boy named Max, who happens to have an eidetic memory, has memorized the Astrogation tables from his uncle’s books, and wants to join the Guild, but is turned down. He lies his way onboard a ship, and through a series of events becomes the only one who can guide the ship home.
• The Star Beast (1954) – A teenage boy has an alien “pet” his great-grandfather had brought back that has grown very large, and is considered a nuisance. A court decides the beast must be killed, but that proves easier to say than to do. It appears that the beast isn’t even aware that people are trying to kill it. Meanwhile, a powerful and hitherto unknown alien species demand the return of one of their own, or they will destroy the Earth. Of course, it is this beast, who is actually royalty to the alien species. One interesting point is that government officials in this story are portrayed sympathetically as intelligent and dedicated.
• Tunnel In The Sky (1955) – In the future humanity is colonizing other planets, and a group of teenagers are taking their final survival test. They are sent to a planet and told that they have to survive for 10 days, But more than 10 days go by with no pickup, and they know something went wrong. So they have to establish their own little society to keep surviving. An interesting note is that the protagonist, Rod Walker, is black. It was never explicitly stated in the text, but Heinlein was firm in stating this. The clue is when the others expect Rod to end up with Caroline, who is explicitly stated to be black. This was Heinlein being subtly subversive. To have a black protagonist for a boy’s story in 1955 in America would be impossible. but Heinlein was completely anti-racist, among other things.
• Time For The Stars (1956) – This is a novel that takes Relativity seriously, which was not common in the 1950s. Researchers have discovered that some twins and triplets can communicate telepathically (and instantaneously), and so when a group of ships is sent out to explore other star systems, one twin is on the ship and the other remains on Earth to provide communication. The twin on Earth ages must faster than the one in space, of course, and eventually the Earth twin dies, But they discover that the connection sometimes passes down through the family, so the protagonist, Tom Bartlett, becomes connected first to his niece, then his grandniece, and finally his great-grandniece.
• Citizen of the Galaxy (1957) – This book is about a future slave trade, which Heinlein strongly hated. The protagonist is a boy who is bought at a slave auction by an old beggar, but the beggar is more than he seems. He is actually spying and gathering data regarding the slave trade. When discovered, he commits suicide, but he had prepared the young boy, Thorby, who then contacts the Free Traders who spirit him away. He has to adapt to this new society, but then is delivered to the Hegemonic Guard. It turns out his “father” (i.e. the man who bought him) was an officer in this organization. And when they run the background checks, they discover that he is the heir to a large conglomerate, and that conglomerate may be implicated in the slave trade.
• Have Space Suit—Will Travel (1958) – Clifford “Kip” Russell dreams of going to the Moon, and enters a contest with that as the top prize. Unfortunately, he wins the somewhat lesser prize of a used spacesuit. The first few chapters focus on him doing repairs and maintenance to make it functional again, and this displays Heinlein’s engineering background. It is more engaging than you might think. Then while wearing the spacesuit he receives a radio message, and he is kidnapped along with an alien called “The Mother Thing” and a young girl who is a genius. The kidnappers are a group of aliens who consider anyone not of their race to be animals. The trio first try to escape on the Moon, but are recaptured, then taken to Pluto, where they succeed in killing the alien kidnappers. Then they are taken to the Lesser Magellanic Cloud to be put on trial to determine if the human race should be allowed to live.
• Starship Troopers (1959) – This is the novel that Scribners rejected, and which brought the Juvenile series to an end. And it bears absolutely no resemblance at all to the movie, to the point that for Heinlein fans the word Verhoeven is considered an obscenity. A young man, Juan “Johnny” Rico joins the military, where he has to grow up and then take part in a war against an insectoid race, but that is all background really. The book is primarily a glorification of military service, which is not surprising given Heinlein’s background. And it focuses on a series of discussions under the heading of “History and Moral Philosophy”, which lets Heinlein expound on his values and beliefs. The novel won a Hugo, but it is an add one given that the plot is secondary to the philosophizing. One of the most controversial ideas is that in this society the right to vote is limited to people who have been in Federal Service. Heinlein said this didn’t have to be military, but the only ones we see are in fact military veterans.

So, these are the Heinlein Juveniles. In my opinion, many of them are quite good reading for adults. The thing that separates them from adult novels in Heinlein’s body of work is the lack of any sex element. That would become prominent in Heinlein’s later adult novels, but it was not something you could put in a book aimed at teenagers, certainly not in the 1950s, and arguably the case today as well.