I am about as ambivalent about this book as I have been about any. It didn't help that nowhere on the materials did it mention that it is part 1 of a 2-part series, and it ends frustratingly abruptly with what some people call a cliffhanger but to me just seems confusing. I also didn't know that the author Connie Willis has set other time-travel stories in this same "universe", and I probably would have read some of the other ones first.
For most of the book it just seemed like a sub-par Doctor Who episode about time travelers observing the Blitz. I appreciated learning some of the extra historical detail but much of the plot action was solving a problem that turned out not to be a problem in the first place, or arranging train schedules or something. It didn't help that I wasn't convinced by the beginning of the story, which takes place in Oxford in 2060 as the time travelers depart, especially because the academics don't act like academics at all. The grad students aren't particularly smart, and there was nothing specifically Oxfordian about anything going on. Michael Crichton's grad students are much more convincing. Also, I'm not convinced by Willis's portraits of the children, who all seem to be either demonic or incredibly whiny.
Once stuff starts to go wrong (or does it?) the plot gets going and there's an efficiently exciting climax as a raid approaches. I enjoyed some cool historical stuff like inflatable tanks, but ultimately I was disappointed to find there's another whole book left. My first thought was that I had somehow missed the last audiodisk! We'll see. If trajectory is any guide I may end up enjoying this yet.