From the days of farmer's bartering for bushels of corn to establishing the concept of credit, this practical guide gets at the root of the subject of money: why it exists and, more importantly, what money really is. THE ABC OF MONEY is an undiscovered gem offering a wealth of knowledge and Carnegie's shrewd philosophies on the subject - a fascinating look at the history of ''debased coin'' and ''greenbacks,'' and the value of currency from one of the great American industrialists.