The book is uninspired and uninspiring, sadly. Its premise is excellent: parallel lives of two prominent military figures, Napoleon and Wellington, who are seemingly destined to clash on the battlefield, and only one would be left standing. It's not just the clash of military leaders, but the battle of worldviews, ideologies, as well.
Unfortunately, the author does not seem to find the right tone for the story - to me, it rang false. Although Scarrow did an excellent job learning everything he could about personal, intimate details of the two men's lives and upbringing and insert them in the narrative, the prose itself is lackluster, the story's style is more that of a high-school essay and less of a novel, full of cliches and trite similes. The dialogues possess none of the wit and sparkle that, I'm sure, real people's conversations must have had. Readable but not more than that.
Another thing - and it is possibly just my own, personal, pet peeve - is that whenever Scarrow writes of people's personal lives, he seems to not be fully comprehending the social aspect of the period. His descriptions of military campaigns are top-notch, those of social interactions a less so. The entiry story of courtship of Wellington and Kitty Pakenham rang false. An unmarried lady scampering about alone, without a chaperone or servant, pretending to be a man's wife, dining out in public at a restaurant with a man who is not her relative or fiance? At the time, she would have been condemned as a harlot. When reading, I had a distinct impression of modern people in fancy dress and powdered wigs. The author though saw nothing wrong about it.
So, the final rating is somewhere in the middle: a good idea spoiled by mediocre execution. Hopefully, other books in the series will be better. I'm not holding my breath though.