The Book of Esther in the Light of History
In 1923, Jacob Hoschander, a professor of cognate languages at Dropsie College (later on the faculty of the Jewish Theological Seminary) wrote a book called The Book of Esther in the Light of History.
It's a brilliant book. Despite the fact that Hoschander was an old style bible critic (though not so "old style" in the 1920s, I suppose), he actually argued very strongly that the events in the Book of Esther were historically real ones. As he writes in his preface:
THE aim of the present book is to interpret the Book of Esther from the historical point of view and to show the historical origin of the Festival of Purim. It is this historical aspect which fundamentally differentiates the present interpretation from all previous attempts at explaining the origin of the Purim Festival on which the Biblical narrative is based, as in none of them has there been suggested an historical reason, drawn from non-Biblical sources, for the danger impending over the Jews during the Persian period. The very fact, however, that outside of the Biblical narrative which attributes this danger to the enmity of a Persian grand vizier toward a single Jewish individual, nothing was known from external historical sources to account for such an event, was reason enough for doubting or denying altogether its historical character. My interpretation, however, is based upon an historical event during the Persian period, well known from non-Biblical sources, the consequences of which must have been disastrous to the Jews of the Persian empire. This event I considered of so great importance for the Jews of the Persian empire that, in investigating the subject, I felt constrained to declare, that if the Book of Esther had never been written, historians might have found out, that during that period the Persian Jews were threatened with complete extermination. The real problem is not, whether such an event did happen, but how the Jews escaped the danger, and its solution is presented, I claim, in the Book of Esther. The historical event, on which the Biblical narrative is based, is treated in the sixth chapter.
Hoschander's book has been out of print for most of a century now, and while it would have been nice had it been available a month and a half ago (in time for Purim), it's back in print now:
It should be up on Amazon.com as well, but apparently that takes a while. I recommend this book highly. Although Hoschander is, at times, very dismissive of rabbinic tradition, his core arguments are solid, and well based in archaeological, classical, and rabbinic sources.