I have a very close personal connection to this number theory textbook. My thesis supervisor studied under Kenneth Ireland in the early 1990s, before the latter's untimely passing. The other day, as I met with my supervisor, he pulled out his copy of A Classical Introduction to Modern Number Theory
and showed me the front cover: signed by Ireland himself. It turns out that Ireland gave his copy of the textbook to my supervisor as a gift some twenty years ago. It felt more than a little strange to leaf through it that afternoon.
This is a great number theory textbook. Time and time again have I returned to the sections on Gauss and Jacobi sums. What a joy it is to live in a world where such beautiful math exists and where it is so expertly explained by authors like Rosen and Ireland. Although it is too late to meet Kenneth Ireland himself, his work in number theory will live on through this wonderful textbook.