(1) Beautiful writing. Really, truly lovely. The following is a description of the Greek mercenaries on the mark:
These watched, amazed, from the highest of the crumbling escarpments, as now a great rash spread over the desert, a river of men, dark under the sun save where the light caught around them, a tawny, leaning giant, a toiling yellow storm bent on blotting out the western sky. It seemed a nation on the march, a whole people set on migrating to a better place. The sparse inhabitants of the Gadinai drew together, old feuds forgotten, and watched in wonder as the great column poured steadily onward, as unstoppable as the course of the sun. It was as grand as some harbinger of the world's end, a spectacle even the gods must see from their places amid the stars. So this, then, was the passage of an army.(2) Kierney did his research. Oh hells yeah, he did. This book basically counts as military fantasy, and it is the best description of phalanx fighting I have ever seen. I'm no expert in ancient Greek warfare, but I know enough to realize when a writer has gotten his details right -- and not only details, but also the strange combination of sheer terror and workmanlike ploddingness that marked phalanx fighting. His descriptions of battle are some of the best I've ever seen.
(A) Is this fantasy? Okay, this isn't really bad, but the book's only marginally fantasy. There's no magic, for one thing, the plot's realistic, and the only real "fantasy" element is the lightweight armor called the Curse of God worn by some of the soldiers. Also there's some weird creatures named Qaf who appear briefly near the end. To be honest, The Ten Thousand might have made more sense of as a historical novel than a fantasy novel. Because . . .
(B) Kearney follows Xenophon's story really closely. The wikipedia summary said this book was "loosely based" on the Anabasis, but that's hogwash. Kearney invents the characters and individualizes their motivations, but he follows Xenophon's plot almost exactly. Which is fine -- unless you happen to be intimately familiar with the Anabasis, in which case there's no suspense or surprises in this book.
Plus, the Anabasis isn't a novel -- it tells of exciting events, but there's no sense (as in novels) of a single plotline following a single thematic thread. "Suspense" isn't really a feature of ancient literature, but one has really come to expect it in modern fantasy novels. Thus the re-telling doesn't translate entirely well.
In addition, there's some rather hollow attempts to widen the interest of the book -- Kearney invents a pretty typical woman character who can be rescued by the love of one of the mercenaries, for example. But, really, the prime interest of this novel is Kearney's fantastic descriptions of battle. That won't work for many readers, and it only worked for me up to a point.
END VERDICT: Glad I read it, but I won't be attempting the other two books in the series . . . unless I plan future research on battle descriptions.