If you’re looking for an introduction to Robert A. Heinlein’s vast corpus of fantastic science fiction, don’t read Sixth Column, read The Moon is a Harsh Mistress. If you’re a Heinlein junkie who’s read all his other stuff and you want a quick, fun read covering the typical Heinlein themes (the able man, war, gee whiz technology, “long live democracy”), then you’ll definitely want to pick up this book.
The basic premise is: the USA has been invaded by “PanAsians,” and the government effectively destroyed. Having subjugated India, the “PanAsians” know how to tie down the USA–lots of labor camps, citizen registration and public executions as punishment for any rebellion. But they also have learned not to interfere with their subjects’ religion(s). One small military base, a research laboratory, has escaped destruction; luckily the plucky soldiers have an able commander and lots of technology the invaders simply can’t match.
From there, it’s just a matter of time. The reader gets to watch how these men build a movement, screw with the “PanAsian” leadership, and eventually free the USA. Of course the technology is hokey and the dialog can be a bit offensive, but it’s realistic (yeah, I think slurs are allowable if they’re marching your family off to the labor camps). This book was written in 1949 and reflects some of the paranoia that Heinlein later gave voice to in Expanded Universe.
But, it’s a fun, quick read and if you like Heinlein, you’ll probably like it. It’s no classic, but not every book can be.