Written for readers with modest mathematical backgrounds, this book contains numerous exercises and examples at varied levels and provides a well-motivated introduction to the classical formulation of class field theory--placing great importance on the explicit numerical example to illustrate the power of basic theorems in various situations. It includes an elementary treatment of quadratic forms and genus theory; addresses when a prime p is of the form x2+ny2; features new coverage of Shimura reciprocity law; and includes simultaneous treatment on elementary and advanced aspects of number theory.