From the reviews: "The book under review . provides an introduction to the general theory of semisimple or reductive groups G, with symmetric space G/K (K maximal compact). . It is . meant for experienced insiders, even as the presentation of the material is excellent and accessible. A well-prepared graduate student would do well with this book. More experienced analytic number theorists will find it enjoyable and spellbinding. . I heartily recommend to other analytic number theorists of a similar disposition." (Michael Berg, MAA Online, December, 2008) "This book is part of a program of the authors to develop a systematic theory of theta and zeta functions on homogeneous spaces, using techniques of harmonic analysis and, in particular, heat kernels. . the book includes many details that would likely have been left for the reader to work out by her/himself in a more streamlined monograph. . all in all, an enjoyable book to read." (Fredrik Strömberg, Zentralblatt MATH, Vol. 1192, 2010)