How many figures from ancient history make promising subjects for modern biography? Julius Caesar heads the list, to judge by the numerous studies of Caesar’s life (and death) that have appeared in recent decades; after him, his Plutarchan parallel, Alexander the Great. Thereafter, names of candidates are harder to summon, since source material — especially the self-explorations or self-revelations that would lend depth and complexity to a biographer’s portrait — is harder to come by.

Nonetheless the ranks of Greek, Roman, and Macedonian biographies has swelled in recent years, as Plutarch’s “Life”-centered approach to the ancient past has grown ever more popular. Anthony Everitt broke new ground in 2002 with Cicero: The Life and Times of Rome’s Greatest Politician, followed eight years later by the astonishing success of Stacey Schiff’s Cleopatra: A Life (now in development as a major motion picture). In more scholarly segments of the book world, biographies of Demosthenes (by Ian Worthington), Galen (Susan Mattern), Josephus (Frederic Raphael), and Seneca (separate studies by myself and Emily Wilson) have appeared during the last five years, along with Augustus and a dual biography of Antony and Cleopatra (both by Adrian Goldsworthy).

Some ancient historians have resisted this momentum and have distanced themselves from biography, even while publishing books that might easily be so classified. Thus Pierre Briant, the renowned French scholar of Achaemenid Persia, began his 1974 study of Alexander by stating “This book is not a biography.” He virtually repeated that assertion in the introduction to his 2003 monograph on Alexander’s Persian opponent, Darius III, published in English earlier this year as Darius in the Shadow of Alexander. “A biography is not only the collection of everything one can and must know about an individual,” he states in the introduction to the English version (quoting medievalist Jacques Le Goff), presumably implying that some deeper psychological insight — a sense of character, a view of the subject’s inner life — is also required.

Briant’s study of Darius is cited as an inspiration by Richard Stoneman, author of a new book soon to be released by Yale (and already available on Kindle), Xerxes: A Persian Life. But unlike Briant, Stoneman embraces the role of biographer, even while acknowledging the difficulties it entails. “A modern biographer…must enter into the mind of his subject,” he writes, “but in this we are hampered by the lack of any kind of introspection or reflexivity in most ancient writings, Augustine and (perhaps) Cicero being the most notable exceptions.” (Seneca the Younger, as I would maintain, ought to have been added to this list.)

This lack of self-revealing sources is an even more acute problem for Persian figures, as Stoneman observes, than for Greeks and Romans. The formulaic portraits of the Achaemenids do not suggest distinctive personality traits, and their recoverable writings consist only of bombastic proclamations inscribed on stones. Animating such figures is a challenging task, as Plutarch discovered when he wrote the Life of Artaxerxes, Xerxes’ successor. “The personality disappears inside the office,” Stoneman remarks of this sole instance, prior to his own, of an attempt at a Persian biography.

Yet the thinness of Persian source material did not stop classical Greek writers from getting inside Xerxes’ head. Herodotus for example created a rich and complex portrait of the king’s character, teased out in imagined encounters between Xerxes and various foils — the exiled Spartan Demaratus, the impetuous Persian warrior Mardonius, and Artabanus, the king’s sober, sagacious uncle. In conversations with these men, Xerxes reveals a strange admixture of audacity, self-doubt, and existential despair, the last displayed in a striking scene at the Hellespont in which Xerxes weeps for the brevity of human life.

Aeschylus too, after fighting against Xerxes at Salamis and perhaps seeing the king in the flesh, tried in the play Persians to analyze the king’s character and motives. In a dialogue between Xerxes’ father Darius, resurrected from the underworld in ghostly form, and mother Atossa, Xerxes is described as a young monarch with over-zealous impulses and an inability to stand up to elder advisors. His senior staff, Atossa asserts, led Xerxes astray by playing on his insecurities, comparing him unfavorably to his revered father. That depiction matches up reasonably well with the Persian council scene at the start of Herodotus’ seventh book, in which Mardonius, seeking to advance his own fortunes, goads and manipulates Xerxes into sanctioning the Greek expedition.

And then there’s the Biblical Book of Esther, with its strange tale of Xerxes’ passion for a Jewish beauty and his resulting rejection of his genocidal vizier, Haman. Some Classicists may have heard the story retold at the Jewish festival of Purim — the carnivalesque Spring holiday at which a public reading of Esther is always prominently featured — perhaps without realizing that its central figure, King Ahasuerus, is none other than our own dear Xerxes, his name transformed from the Persian Khshayarsha into a more Hebrew-friendly version, just as it had also been Hellenized for Greek tongues.

Stoneman, in his attempt to reconstruct Xerxes’ personality, confronts each of these mythic accounts, as well as other, more recent fictions, including a novelistic retelling of Xerxes’ reign by Gore Vidal, Creation. Pop-culture fans will be disappointed, however, that he ignores altogether the recent 300 movies and the graphic novel on which they are based — perhaps deeming, with some justification, that their bizarre portrayal of an androgynous, multiply pierced Xerxes, suffering from childhood trauma after watching his father killed before his eyes and transformed into a deity by his dip into a supernatural pool, bears no relation whatever to the ancient literary record.

The legends and quasi-historical tales found in Herodotus, Aeschylus and the Bible present a greater problem for Stoneman here than did a similar body of material in his superb Alexander the Great: A Life in Legend (2007). There, his topic was the Alexander tradition, which by definition is made up of half-truths and mythicizations. Here, however, in a book that proclaims itself a biography, the question of historical veracity matters — and it’s a question Stoneman is often hard put to answer, when he even raises it at all.

Let us take the tale of Masistes’ wife as an example, the last view Herodotus gives us of Xerxes in the Histories. In this racy, salacious bedroom intrigue, Xerxes becomes besotted first with the wife of his brother Masistes, then with that woman’s daughter, his own niece. His reckless passion leads to gruesome reprisals and drives his brother into revolt. He appears to have abandoned the responsibilities of rule in favor of erotic passion, a foreshadowing of the decline that, in Greek eyes, was destined to afflict the Persian state as a whole. But the neatness of that very foreshadowing calls the story into question.

Stoneman hedges his bets as to whether to give credence to the tale. “Herodotus tells the story in masterful detail; but whether all the details are true is another matter,” he comments. Yet he never returns to that question. A short while later, however, he refers to “Xerxes’ disastrous affair with his niece” as a historical certainty. He never explicitly endorses the portrait bequeathed to us by Herodotus — that of a lovestruck and decadent monarch, who retreated into affairs of the boudoir and harem after his greatest military undertaking came apart at the seams — but he never challenges it either, and by retelling it at some length, in a chapter entitled “Family Romances,” he lends it a good deal of substance.

Is the tale of Masistes’ wife, or indeed any of Herodotus’ Xerxes material, fair game for a biographer? Helen Sancisi-Weerdenburg, in an article cited by Stoneman but apparently not taken to heart by him, convincingly answered this question in the negative. “Although Herodotus’ portrayal of Xerxes is persuasive and beautifully elaborated, it contains very little that a historian could use as hard evidence for the character of the king,” she asserted in “The Personality of Xerxes, King of Kings,” recently reprinted in Brill’s Companion to Herodotus. Greek mythic ideas, story-patterns, and cultural prejudices helped to reshape such tales before Herodotus heard them or wrote them down — if indeed they had a historical basis to begin with, which is far from certain.

Complicating Stoneman’s discussion of the tale of Masistes’ wife is his juxtaposition of the Biblical Book of Esther, another story in which Xerxes is revealed as a passionate and sensual lover of women. Here at last Stoneman brings his source-critical skills to bear, asking (in a rubric) “Is It History?” and advancing cogent reasons why it is not. But if this legend falls, does that not call the Herodotean tale of Masistes’ wife, nearly contemporaneous with it, more deeply into question? The reader comes to the end of Stoneman’s chapter on “Family Romances” wondering whether Xerxes had any of these at all.

One wants to forgive these shortcomings because there is so much else in this book that is so well done. Stoneman’s overview of the Persian Empire, his handling of the tricky question of Achaemenid religion, and his close analysis of the ruins at Persepolis — a site that he has had the privilege, rare in the era of Shiite-led Iran, of studying first-hand — are detailed, intelligent and beautifully written, the best such discussions I know of anywhere, and can be highly recommended to readers of Herodotus who are newcomers to Persian history. All these discussions are accompanied by admirably brief and lucid footnotes, a model (and increasingly rare) style of citation directed at a non-specialized readership.

The great oddity of this book, then, is that it has been cast as “A Persian Life” when so little of that life can be recovered. Stoneman seems to have followed the siren call of Plutarch into framing his material as a biography when it seems better suited to a collection of Xerxes lore, similar in spirit to his earlier treatments of Alexander. Stoneman has mastered a huge array of that lore, including modern operas, plays and novels along with the ancient sources. But all of this put together still does not add up to “A Persian Life.”

Stoneman is a remarkable writer who has had a remarkable career. Formerly a Routledge editor, he has followed his passion for Greek and Near Eastern literature as author, independent scholar, and Mediterranean tour guide, and recently won appointment as honorary visiting professor at the University of Exeter. He learned Old Persian as a way to get closer to the Achaemenid monarchs, imitating in this Themistocles, whose versatility and ingenuity he shares. He has produced much fine work both as a translator and an interpreter of ancient legends and lore, and doubtless will continue to do so.

But by heading down the path of biography, rather than the study of lore and Nachleben, Stoneman has taken a wrong turn into a historical cul-de-sac. Given how little we know of Xerxes from Persian sources, and how many uncertainties attend the Greek and Hebrew ones, the task of writing his “Persian Life” was doomed from the start. Oddly, Stoneman’s book best succeeds during the sections in which Xerxes himself, its ostensible subject, is off the scene — as he is for long pages, even whole chapters, at a stretch.

James Romm is James H. Ottaway Jr. Professor of Classics at Bard College in Annandale, N.Y., and author of several books, including Dying Every Day: Seneca at the Court of Nero. He reviews regularly for the Wall Street Journal, the London Review of Books and the Times Literary Supplement.

The views expressed in this article are those of the author and do not reflect the views of the Paideia Institute.