From the reviews:
"...a fine book ... treats algebraic number theory from the valuation-theoretic viewpoint. When it appeared in 1949 it was a pioneer. Now there are plenty of competing accounts. But Hasse has something extra to offer. This is not surprising, for it was he who inaugurated the local-global principle (universally called the Hasse principle). This doctrine asserts that one should first study a problem in algebraic number theory locally, that is, at the completion of a vaulation. Then ask for a miracle: that global validity is equivalent to local validity. Hasse proved that miracles do happen in his five beautiful papers on quadratic forms of 1923-1924. ... The exposition is discursive. ... It is trite but true: Every number-theorist should have this book on his or her shelf."
(Irving Kaplansky in Bulletin of the American Mathematical Society, 1981)
Reader's review:
There has never been in any time a book in any language that can put on a par with Hasse's monumental refrence Number theory . It is a text as well as a great refrence, and it is sad that those people at springer verlag not just printed on a low quality papers, they put it altogether out of print.
