There's an old 1948/52? edition available as a scanned PDF which can give you an idea if you want to buy the updated version: http://www.fee.org/pdf/books/Economics_in_one_lesson.pdf.
At a higher level, The Road to Serfdom by Friedrich von Hayek is also short but unlike the above quite dense. Most useful (to me) for applying information theory to command economies. Rather apropos to the situation in the US today, it was published in 1944 and dedicated to "The socialists of all parties". It was intended as a warning to the British socialists of the day who were about to take over and remake their country, warning them of a variety of things, some of which they found out the hard way, plus the demonstrable even back then danger of concentrating so much power at the top (too easy for idiot thugs to take over, e.g. Stalin, "Those who are good at acquiring and exercising discretionary powers in government are usually the most ruthless and corrupt individuals." (Wikipedia)). http://www.amazon.com/Road-Serfdom-Fiftieth-Anniversary/dp/0...
Check out http://en.wikipedia.org/wiki/The_Road_to_Serfdom#External_li... for the Reader's Digest condensed version (Hayek was amazed at how good it was) and there's even a cartoon version that I reviewed and found to be quite good.
After the above two you'll be oriented for a variety of much larger tomes, from the classic The Wealth of Nations to e.g. von Mesis' Human Action.
Actually the first book I'd recommend would be The Worldly Philosophers, a readable history of economics
https://www.amazon.com/Worldly-Philosophers-Economic-Thinker...
A couple of more right-leaning books - Hayek, The Road to Serfdom https://www.amazon.com/Road-Serfdom-Fiftieth-Anniversary/dp/...
Friedman, Capitalism and Freedom https://www.amazon.com/Capitalism-Freedom-Anniversary-Milton...
Less right-leaning
The Marx-Engels Reader https://www.amazon.com/Marx-Engels-Reader-Second-Karl-Marx/d...