The book is aimed at students of law, public economics, finance theory and accounting, as well as judges and legislators. The book presents in a comprehensive and detailed manner the U.S. tax system and its terms of art. It explains how the system works and how the tax liability of the taxpayers is determined. The book also discusses, in a structured, analytical, and friendly language, the question of "why": why Congress and the courts have established these multiple statutory rules and precedents and what is the logic underlying them; what are the economic and social principles that help in understanding the complex and interdisciplinary system of the American tax structure. In addition, the book explains the basic rules of foreign tax systems, the understanding of which is essential for practicing tax in our "global village". The authors have been engaged in researching and teaching tax law, public finance, and fiscal legislation for over forty years in the U.S. and around the world. Their broad perspective and professional experience allows them to offer, in addition to describing the current system, constructive criticism and alternatives as well, which can lead to a dramatic improvement in the tax system, to the reduction of social gaps and poverty and to increased economic efficiency, which eventually will be transformed into sustainable economic growth.