The story itself was intriguing with the mixture of medieval and modern equipment and surroundings. Trying to evade a war is never easy, but in a way the plot was given away from the start. The search for the artefact felt glossed over. Probably the biggest problem of the book was that the author was trying to keep it short, but by doing that was afraid to get into anything in detail. Most of the book was taken up by talking, plotting, without anything much actually happening.
The Doctor seemed to play a minor character here, and I found that that must have been because the author didn't have a good grasp of him. It was a bit strange, because one of her other books, The Way Through the Woods is actually one of my favourite Doctor Who books.
Clara was more of a central character in the story, getting mixed up in trying to stop a war. She seemed to have gone rogue, acting on her own.
Bernhardt was the author's own character. For some reason, his parts were in first person. This constant change of perspective was very strange. I do see the point in it, but the story was disjointed because of it.
Overall, it was an interesting story, but lacked depth and excitement. Hence only three stars, since it wasn't bad, just not enough.