Salt: A World History - A fascinating history of humanity's favorite mineral. Wars have been fought over it, it sustained whole economies ... you'll be surprised to learn just how much of human history has been influenced by salt.
A Short History of Nearly Everything - One of my favorite books. Bryson tells the story and history of science through amazing discoveries and stories about the quirky people who made them.
Homage to Catalonia - A mostly auto-biographical account of George Orwell's time fighting for the communists in the Spanish Civil War.
Capital: Vol. 1 Marx's seminal work and a logically sound criticism of capitalism. Whether or not you agree with his proposed solutions, his criticism is spot on. Depending on how leftist you are, you may have already read The Communist Manifesto. It's a nice introduction to Marx's ideas, but you should really go straight to the source and just read Capital.
Why We Believe What We Believe - The neurology of belief, what could be more interesting? The authors go into great detail on how belief happens at the neurological level, as well as summing up nicely all sorts of findings from differing fields relating to belief. The most interesting part is the research the authors themselves conducted: fMRI scans of people praying, Buddhist monks meditating, Pentecostals speaking in tongues, and an atheist meditating.

>They're anarchists. Have you ever heard of anarchist armies?

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Here are two more of Chomsky's recommendations gleamed from Understanding Power: The Indispensable Chomsky
(which I highly recommend):

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