Barry Simon 
Representations of Finite and Compact Groups [PDF ebook] 

Barry Simon is the author of many well-known books, including such classics as Methods of Mathematical Physics (with M. Reed) and Functional Integration and Quantum Physics. This book, based on courses given at Princeton, Caltech, ETH-Zurich, and other universities, is an introductory textbook on representation theory. Two facets distinguish the approach. First, the book is relatively elementary, and second, while the bulk of the books on the subject is written from the point of view of an algebraist or a geometer, this book is written with an analytical flavor. The exposition centers around the study of representation of certain concrete classes of groups, including permutation groups and compact semisimple Lie groups. It culminates in the complete proof of the Weyl character formula for representations of compact Lie groups and the Frobenius formula for characters of permutation groups. Extremely well tailored both for a one-year course in representation theory and for independent study, this book is an excellent introduction to the subject which is unique in having so much innate beauty so close to the surface.