Pagan Passions by Randall Garrett, Science Fiction, Adventure, Fantasy

War on any scale was outlawed, along with boom-and-bust economic cycles, and prudery -- but no change was more startling than the face of New York, where the Empire State Building has become the Tower of Zeus

In this altered world, William Forrester is an acolyte of Athena, Goddess of Wisdom, and therefore a teacher in this case of a totally altered history . . . but the fate that awaits him is a thing even more fantastic than the circumstances we've described