The Moon is a Harsh Mistress. I've mentioned this novel, and the fact that it prominently features Heinlein's own libertarian views, in a previous post.
By 2075 Luna (what most lunar citizens or "Loonies" call the Moon) has a thriving population. Although originally begun as a prison colony, the vast majority of Loonies are now former prisoners (many for political reasons) or are the descendants of prisoners. Luna's past, as well as the fact that the ratio of men to women was 10 to 1 in Luna's early days and 2 to 1 by 2075, has strongly affected their culture (the Loonies responded to their uneven demographics with some unorthodox marriage arrangements).
Most Loonies make their living as farmers; growing grain in underground tunnels and shipping the grain to Earth via an electromagnetic catapult. The catapult, like most of Luna's systems, is ran by an advanced HOLMES IV computer that is constantly being expanded to take on new tasks. For reasons unknown to Manuel, the computer's repairman, the computer gradually attains sentience. Manuel eventually names his electronic friend "Mike".
Luna is governed by the Lunar Authority; an entity under the control of Earth's Federated Nations. Although most Loonies are supposed to be free citizens rather than prisoners, the Warden (the local representative of the Lunar Authority) effectively has dictatorial powers. Manuel and Mike stumble into the political movement to overturn the Warden and become involved with a group of would-be revolutionaries led primarily by Wyoming Knott and Professor Bernardo de la Paz. Although initially reluctant to join, Manuel is convinced by Mike's calculation that, at the rate grain is being shipped to Earth to meet the Lunar Authority's ever-rising quotas, Luna will rapidly run out of water and organic material and will starve to death.
With the help of Luna's primary control computer (and the only sentient computer ever known), getting rid of the Warden may be relatively easy. But the nations of Earth have become dependent on Luna's grain, and the poorly-equipped Loonies don't seem to have a chance against the the nuclear-armed warships of the Federated Nations. But Loonie ingenuity, and Mike's plan to use the electromagnetic catapult to hurl tons of Moon rocks at the Earth (which would hit with the force of small nuclear warheads), just might give the Loonies a chance.