The Scribner's juveniles
James Gifford wrote, "It is not often recognized that [the juveniles] are a reasonably consistent 'Future History' of their own". The dozen novels do not share any characters and do not form a strict chronological series; the later novels are not sequels to the earlier ones. They nonetheless tell a single story of space exploration. The first novel, Rocket Ship Galileo, is about an effort to reach the Moon. The next few (through The Rolling Stones) revolve around interplanetary travel within the solar system. The next few (Starman Jones through Time for the Stars) revolve around various versions of the early phase of interstellar travel. In the next novel (Citizen of the Galaxy), interstellar travel is well-established and easy for humans, and the central problem is one of the maintenance of law and order in the galaxy. The protagonist of the next and last Scribner's juvenile, Have Space Suit—Will Travel, travels to the Lesser Magellanic Cloud and interacts with an intergalactic civilization. The last book submitted to Scribner's, Starship Troopers, portrays an interstellar war between mankind and several other species.
The intended readership was teenage boys, but the books have been enjoyed by a wide range of readers. Heinlein wanted to present challenging material to children, such as the firearms for teenagers in Red Planet. This led to "annual quarrels over what was suitable for juvenile reading" with Scribner's editors.
Groff Conklin wrote in 1955 that "Nobody but nobody can beat Heinlein in the writing of teen-age science fiction". Jack Williamson wrote: "[An] inspiring theme of space conquest unifies the dozen Scribner's titles ... The books, taken together, tell an epic story of the expansion of mankind across the planets of our own Sun and the stars beyond. ... a generally consistent story of the future conquest of space. The first, Rocket Ship Galileo, begins in a backyard shortly after World War II, with three boys testing a primitive rocket motor. The last, Have Space Suit—Will Travel, ends with the triumphant return of its young hero from the Lesser Magellanic Cloud... Nobody has written a more convincing and inspiring future human epic."