Along with the excellent recommendations here, I would add "The Worldly Philosophers" by Heilbroner (http://www.amazon.com/Worldly-Philosophers-Lives-Economic-Th... (http://www.amazon.com/Worldly-Philosophers-Lives-Economic-Thinkers/dp/068486214X)) for a slightly different angle. It covers a wide range of famous economists and describes the high points of their theories along with some biographical detail, in a very engaging style. It's the economics version of "Men Of Mathematics", which is also a fascinating book.
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