What is the author's style in Citizen of the Galaxy by Robert A. Heinlein?

Citizen of the galaxy was published in 1957 as a juvenile novel. While the book deals with complex themes and is appropriate reading for adults, the fact remains that Mr. Heinlein was hired to write a novel for twelve-year-old boys and Citizen of the Galaxy was the result. While the writer never condescends to his audience, he uses straightforward language that is easily comprehended by an intelligent sixth grader—language that is common to everyday speech and rarely assumes that the reader is familiar with any literary or historical references.