Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Hard science and plot combine to teach the reader.

Sci-fi has always had the intention, either primary or secondary, of chanllenging, undermining or destroying the reader's world view. In "The Moon is a Harsh Mistress" it appears to be secondary, despite the author's obvious Marxist sentiments. Because life on the moon is not life on earth, Heinlein is freed by the science of space to create a fictional social order where, at the outset, air is not free. The juxtaposition of science and plot continues until the reader should see that he or she is in fact learning something of physics and astrophysics. Of particualr interest is the book's description of weapons systems crafted by, sare I say it, crafty moon residents. A mass driver that takes advantage of the disparate sizes of the moon's gravity well as opposed to that of the earth is a wonderful "Popular Science" gizmo. Also of note is the clever cell system administered by computer for the lunar revolutionaries.