A book on any mathematical subject beyond the textbook level is of
little value unless it contains new ideas and new perspectives. Of
course it helps to include new results, provided that they give the
reader new insights and are presented along with known old results in a
clear exposition. It is with this philosophy that the author writes this
volume. The two subjects, Dirichlet series and modular forms, are
traditional subjects, but here Goro Shimura treats them in both orthodox
and unorthodox ways. Regardless of the unorthodox treatment, the author
has made the book accessible to those who are not familiar with such
topics, by including plenty of expository material. The book contains
never before published elementary proofs. It is self-contained, and
suitable for use in a classroom setting.