The principal object of this multi-volume treatise is to provide, in a self-contained manner, comprehensive coverage of the mainstream of group representation theory. The audience for these volumes consists of aspiring graduate students and mature mathematicians working in the field of group representations. No mathematical knowledge is presupposed beyond the rudiments of abstract algebra, set theory and field theory; however, a certain maturity in mathematical reasoning is required. Apart from a few obvious exceptions, the volumes are entirely self-contained. The style of the presentation is informal: the author is not afraid to repeat definitions and formulas when necessary. Many sections begin with a nontechnical description and special effort has been made to render the exposition transparent.