The purpose of the book is to present the reader with five of the main results on the structure of rings of algebraic integers as Galois modules and to relate these to other questions of arithmetical interest. Technicalities are avoided without sacrificing generality and enough material is covered to allow the reader to tackle the current literature on the subject. Partly based on notes of lecture courses by leading figures in the field, the book should be accessible to any student who has taken a standard one year course in algebraic number theory. Many exercises are included.
