H. Koch 
Algebraic Number Theory [PDF ebook] 

From the reviews: "… The author succeeded in an excellent way to describe the various points of view under which Class Field Theory can be seen. … In any case the author succeeded to write a very readable book on these difficult themes." Monatshefte fuer Mathematik, 1994"… Number theory is not easy and quite technical at several places, as the author is able to show in his technically good exposition. The amount of difficult material well exposed gives a survey of quite a lot of good solid classical number theory… Conclusion: for people not already familiar with this field this book is not so easy to read, but for the specialist in number theory this is a useful description of (classical) algebraic number theory." Medelingen van het wiskundig genootschap, 1995