From the reviews of the second edition:
This book is a thorough self-contained introduction to algebraic number theory. ... The book is aimed at graduate students. The author made a great effort to make the subject easier to understand. The proofs are very detailed, there are plenty of examples and there are exercises at the end of almost all chapters ... . The book contains a great amount of material, more than enough for a year-long course. (Gabor Megyesi, Acta Scientiarum Mathematicarum, Vol. 69, 2003)
There is a wealth of material in this book. The approach is very classical and global. ... the author keeps his presentation self-contained. The author has made a real effort to make the book accessible to students. Proofs are given in great detail, and there are many examples and exercises. The book would serve well as a text for a graduate course in classical algebraic number theory. (Lawrence Washington, Mathematical Reviews, Issue 2002 e)
Ribenboims's 'Classical Theory of Algebraic Numbers' is an introduction to algebraic number theory on an elementary level ... . Ribenboim's book is a well written introduction to classical algebraic number theory ... and the perfect textbook for students who need lots of examples. (Franz Lemmermeyer, Zentralblatt MATH, Vol. 1082, 2006)