The narrative follows the bare bones of Arthurian Legend, stripped of magic but with trickery and storytelling aplenty. Gwyna/Gwyn (her male self) is thick in the midst of the story, giving a new perspective to the characters and shedding light on the fact that the Arthur of Myrddin's stories is a far cry from the actual Arthur.
I had trouble getting into this, although it's a fairly quick read, aimed at middle schoolers. It was hard to find a sympathetic character; nobody fell into a particularly flattering light in this version of the story. However, that's also part of what made it interesting. The best thing about this book is the way it explores the birth and growth of myths and legends, and how sometimes you just can't let the truth get in the way of a good story.
Overall I enjoyed this, but it was far from my favorite reimagining of the Arthurian mythos. I'm not sure how I feel about it as an introductory story for this legend; it's rather depressing although the ending is not a total downer. It's worth checking out if you want a unique perspective on the stories.
Philip Reeve's website is here.