So, here's a quick, reasonably fun read—a young adult sci-fi adventure called Martians Abroad. The author, Carrie Vaughn, is known for her bestselling Kitty Norville books, a series of adult urban-fantasy stories about a werewolf who moonlights as the host of a Denver radio show. But in Martians Abroad, Vaughn tries her hand at the old Robert A. Heinlein genre of science-fiction "juveniles."
And, as I said, the book isn't bad. It tells the story of a teenaged girl named Polly who, together with her twin brother Charles, is forced by her parents to leave her beloved Martian colony and take classes at the Galileo Academy, a prestigious boarding school back on humanity's home planet of Earth. Eventually, she starts to fit in, sifting the snooty earthlings to find a few real friends—only to stumble on a plot to use the school's students as pawns in an interplanetary conspiracy.
Unfortunately, if Martians Abroad doesn't prove to be a bad book, it also doesn't prove to be a good book. What Carrie Vaughn has written is something around the level of movie-theater popcorn. You don't mind it while you're consuming it, but the stuff doesn't last. The book presents itself as a reimagining of Heinlein, with Polly and Charles a wink toward Poddy and Chuck in his 1963 Podkayne of Mars. But what the reference to Heinlein mostly does is force a question into the reader's mind: Why is it so hard to write that kind of book? Why can't anyone else do what Heinlein did?
Certainly enough science-fiction authors have tried to produce works in the mode of Heinlein's early work, from Poul Anderson to S.C. Sykes, Spider Robinson to John Scalzi. Joe Haldeman—a talented writer and acclaimed author of The Forever War (1974)—sat down in cold blood to imitate Heinlein with The Accidental Time Machine and Marsbound in the 2000s, and who remembers the books? A typical Heinlein novel looks like something anybody else could do—and proves something that nobody else can do. Somehow, in the writing of juveniles, only Heinlein gets away with being Heinlein.
Or perhaps we should expand the collection a little. To refer to Heinlein's juveniles is usually to speak only of the twelve early novels for young readers he published with Scribner's, beginning with Rocket Ship Galileo in 1947 and ending with Have Space Suit—Will Travel in 1958. His 1959 Starship Troopers is sometimes counted as a juvenile, as well. The original manuscript, however, was rejected by Scribner's, and when Heinlein changed publishers, he would begin by revising the book into something aimed at a more adult audience—announcing that he was done with the juvenile genre. (This may be one reason that he always refused to call his subsequent Podkayne of Mars a juvenile. Another reason may be the original ending he wrote for the book, in which the teenage heroine Poddy dies.) For that matter, Heinlein wrote several supposedly adult books in that era, at least two of which match the feeling and tone of the juveniles: Double Star (1956) and The Door into Summer (1957).
Certainly his best-known and most successful books came after the decision to write entirely for an adult audience, with Stranger in a Strange Land in 1961 and The Moon Is a Harsh Mistress in 1966. And in such books as Farnham's Freehold (1964), he clearly felt freer to express the libertarianism that had been implicit in all his earlier published work.
And then there's the sex. The Door into Summer and Methuselah's Children (1958) hinted that Heinlein supported what used to be called "free love," and it came to full display in books from Glory Road (1963) to his gibe at sci-fi feminism in Friday (1982). And then there are the "Lazarus Long" books that begin with Time Enough for Love (1973) and last through to Heinlein's final book, To Sail Beyond the Sunset (1987). Most of what Heinlein wrote after 1958 explores ideas that are more interesting, more profound, in certain senses, than any of his early work. But at some point, even his most fervent fans want to return to books where the hero doesn't use time travel and advanced technology to have sex with his mother, his granddaughter, and his own clone. Or his computer made flesh.
In other words, sometimes we need the early work—Heinlein's juveniles and his pleasant adult stories from the 1950s. So many authors think that they can do what he did, and perhaps the reason is that the prose is so artless. He does have a minor talent for aphorism: "Specialization is for insects." "Progress isn't made by early risers. It's made by lazy men trying to find easier ways to do something." "When a place gets crowded enough to require IDs, social collapse is not far away." But his sentences are mostly in the category of "invisible prose," never rising high enough or falling low enough that the experience of reading is interrupted by notice of the writing.
More to the point, there's something sweet, almost guileless, about the books—and those qualities are the ones that prove hardest for Heinlein's imitators. His letters show a man overflowing with ideas about science and the future, and he always knew how to use those ideas to shape a science-fiction story. Not that the ideas were always good ones. The technicalities of terraforming in Farmer in the Sky (1950) are miles better than the goofiness of the prepubescent alien creature in The Star Beast (1954), and the interstellar politics of Citizen of the Galaxy (1957) are much more satisfying than the interplanetary struggles of Between Planets (1951). The least science-y is probably Double Star, about an actor who stands in for a galactic leader, and the most science-driven is Time for the Stars (1956), which explores the consequences of relativity.
Through nearly all of them, however, there's a kind of easiness. Relations between the sexes are fraught but not problematized. The details of enterprise are assumed to be interesting, in themselves—whether it's the experience of young military cadets in Space Cadet (1948), commercial trade in The Rolling Stones (1952), or life on a brutal alien world in Tunnel in the Sky (1955). There's no gap between will and action, as the young people of Heinlein's juveniles come to believe that adulthood is devotion to something they realize they want to do. This is the origin of what I called the books' guilelessness—for that worldview is innocence, down at its root, even when the grand theme of a book is slavery, war, or survival in harsh circumstances.
Carrie Vaughn can simplify her plots and prose, moving from her steamy werewolf books to her new young adult book, Martians Abroad. But she can't seem to reach the sweetness and guilelessness that permeates those early Heinlein novels. Maybe the difference is captured in the publishers' change of genre identifier, from "juvenile" in the 1950s to "Young Adult" now. Heinlein's children are more mature in some ways than those of his imitators, and yet younger in other ways. Being human isn't an insoluble problem for them. It's a puzzle that has a solution.
Of course, what Heinlein wrote was science fiction, which means that the human puzzle and its solution appear against a background of futuristic science. But that's just the story, which any competent sci-fi writer could imitate. What made Robert Heinlein inimitable was the easiness of the people in those stories.