On Amazon.com: Economics in One Lesson: The Shortest and Surest Way to Understand Basic Economics (1946)
“…the whole of economics can be reduced to a…single sentence. The art of economics consists in looking not merely at the immediate but at the longer effects of any act or policy; it consists in tracing the consequences of that policy not merely for one group but for all groups.“
You can also download a free PDF version from the Mises Institute.
Or you can enjoy this easy-to-read-in-a-web-browser version courtesy of Steven Shaw.