The main story of the book is about Ash, the nineteen-year-old female leader of a mercenary company in late 15th century Europe. Her story starts out as historical fiction (and would be excellent as that alone), before turning by degrees first into alternate history and then into outright fantasy. This happens so smoothly as to never jar the reader's suspended disbelief. There is a frame-tale connecting the episodes of Ash's story: the pretense that we are reading a collection of translated historical documents, complete with correspondence between the historian and his publisher in the fall of 2000. This starts out as a joke and becomes a scholarly/conspiratorial thriller, a la Foucault's Pendulum or The Eight, and by the end of this volume is impinging on Ash's plot. And both plots contrive to end with cliff-hangers which do not seem contrived. (In fact, almost every chapter in Ash's story ends in a cliff-hanger. And it works.)
The depiction of the military life in western Europe in the 1470s is splendidly accurate (I'd bet money she's read J. R. Hale), except that she's modernized the swearing (for which her historian apologizes). The period's mixture of punctillio and crudity is also convincingly captured. Some episodes in Ash's story will seem very mysterious to most readers; those familiar with Mithraism will find them just as mysterious, but much more tantalizing. There are some dubious English-Latin puns.
There are three problems with this novel.
First, the cover artist obviously hadn't read even the first page of the story.
Second, Gentle is pulling off such ridiculously difficult tricks so slickly that, though I don't even want to write fiction, I was consumed with jealously whenever I let myself think about what she was doing to me. Fortunately, she didn't leave me much opportunity to do this while reading the book, but afterwards I stewed and fumed in a green funk. It was worth it.
Third, I really, really want to know what happens next, and I'm stuck for months at least. (Amazon says the next book is coming out in February 2000, but is very unreliable about such things; Avon's web-page says nothing.) This is simply cruel, but at least it will give me a chance to read Gentle's other books.