A book about forgotten realities. This is perhaps the best description of this work. Its title, A Legal Theory of Economic Power, is very revealing in this sense. The old times of antitrust law, centered on market rationality, are gone. Economic power is pervasive in society and cannot be treated as a mere economic phenomenon, based on market rationality paradigms. There are many and very important ‘forgotten realities’ that stayed out of this treatment. Therefore, a theory of economic power must be treated as such, as a general theory. The reference to antitrust law must nowadays be historical. This does not mean that, when treating power created in the market, the theoretical tools should not include classical ‘antitrust’ discussions, though in a revised and critical version. That is what this book tries to do. Power with legal roots and social roots is also treated, however, with different theoretical paradigms. Through them, some of the ‘forgotten realities’ are included and treated. Through them, the reader can also understand another fundamental aspect of the concentration of economic power: its influence on social and economic development patterns. An intended general theory of economic power. That is what the title says and that is what the book intends to be. Too pretentious? That is an answer to be given by a critical reader after reading the book, as long as he/she remains impartial, i.e., allows himself/herself to read the book free from the ‘shadows of the past’, the past of the old ‘market rationality-based’ antitrust law.