I love this whole series. It's set in a time for the Celts, when there were no gender differences, no preconceptions of how a man or a woman should act or what was "masculine" or "feminine". It's about a clash of civilisations, the patriarchal Roman and the often matriarchal Celtic at the time of the Roman invasions. It's wonderfully written, with heroes and villains on both sides. It's also the story of how a violent occupation by a foreign army intent on destroying an entire culture succeeded at an enormous cost for both sides. The characters are so vivid, and I keep reading even though I know how it will end.