Until recently, no ancient historian was more widely read than the first-century soldier-statesman Flavius Josephus, the greatest source of our knowledge of the Holy Land "between the Testaments." In many a Victorian home and American Sunday-school library, a copy of William Whiston's translation of Josephus' works, first published in 1737 and reprinted more than 200 times since, held pride of place next to the Scriptures.

Yet to his own people Josephus remained a pariah—a man who betrayed them in the hour of their...