Foundations of Economics Analysis, by Paul Samuelson
Economics, by Paul Samuelson (and William Nordhaus) or here for the original.
Maybe I should at least mention this for historical reasons. The book is very old by now (though it has seen some updates with Nordhaus becoming a co-author on later editions), but it's amazing how many Nobel laureates in economics cite this book as an inspiration to go into economics---many of them coming from a background in math.
From Roger Myerson's prize biographical,
I have always loved to read about history and found a fascinating beauty in historical maps. But I hoped for something more analytical, and so I was naturally intrigued when I first heard about economics. I began reading Paul Samuelson's basic economics textbook in a high school vacation. When I got to college, I chose to concentrate in economics and applied mathematics...
From James Heckman's prize biographical,
Samuelson's Foundations of Economic Analysis, was an exciting experience that shaped my desire to learn more economics...
From Samuelson's biography, the mention this about his textbook:
His Economics: An Introductory Analysis, first published in 1948, has become the best selling economics textbook of all time. The textbook has sold more than a million copies and has been translated into French, German, Italian, Hungarian, Polish, Korean, Portuguese, Spanish and Arabic. It is now in its fifth edition. "The book's emphasis on different themes has changed with the changing of the nation's economic problems," wrote Business Week in 1959. "The first edition was dominated by the end-of-the-war worry that widespread unemployment would return... later editions put growing stress on fiscal and monetary controls over inflation. In the later editions Samuelson has worked toward what he calls a 'neoclassical synthesis' of ancient and modern economic findings. Briefly, his synthesis is that nations today can successfully control either depression or inflation by fiscal and monetary policies... Some economists feel that Samuelson's book... is really his greatest contribution. It has gone a long way toward giving the world a common economic language."