The Moon Is a Harsh Mistress
From about 1961 ("Stranger in a Strange Land") to 1973 ("Time Enough for Love"), Heinlein explored some of his most important themes, such as individualism, libertarianism, and free expression of physical and emotional love. Three novels from this period, "Stranger in a Strange Land", "The Moon Is a Harsh Mistress", and "Time Enough for Love", won the Libertarian Futurist Society's Prometheus Hall of Fame Award, designed to honor classic libertarian fiction. Jeff Riggenbach described "The Moon Is a Harsh Mistress" as "unquestionably one of the three or four most influential libertarian novels of the last century".