Heinlein was my introduction to the genre thirty-some years ago, and I read all I could get my hands on back then. Even with the political speeches, Heinlein remains the most approachable of writers. He's not beating the reader about the head with libertarianism - the politics is integral to the story, in some cases, it is the story.
The Moon Is A Harsh Mistress introduced the concept of "rational anarchism", which had existed but had no name up to that point. Briefly, the rational anarchist realizes that some government is necessary, but any government is dangerous, and must be watched as closely as a rabid dog.
The plot follows the citizens of Earth's Moon, as they attempt to avoid a looming food shortage by throwing off the shackles of the World Government that keeps them enslaved and exiled. Manuel, a computer technician, joins up with Wyoming ( a professional surrogate mother turned political agitator) and Professor de la Paz as the first cell of a revolutionary movement. The story of Luna's revolution is told with the terrible costs of war in mind, but also with the type of detail that makes a compelling read. We know from the first page that the 'Loonies' are successful, but getting there is all the fun.
The Loonies, mostly miners and farmers, speak in a mixture of 'Strine' and 'authentic frontier gibberish', heavily influenced by Soviet and Russian speech patterns and idioms. This makes it a little hard to follow the narrator until the reader hits his stride. Also, the novel was written in the Sixties, so you're not going to see a lot of sex and violence - though the depictions of polygamy were very shocking back then!
Many Science Fiction writers have an appreciation for liberty - David Weber, Orson Scott Card, and El Neil spring to mind. It must be that longing for the freedom of space, (the final frontier, as some wag put it) awakens the yearning for pure, God-given freedom. Possibly, it's the other way around.
For pure SF fun with a good dose of 'classical liberal' thought and economics, Robert Anson Heinlein can't be beat, and The Moon Is A Harsh Mistress is one of his best.