Blackout/All Clear - Willis

This is a 2011 Hugo Nominee

The basic idea here is that sometime in the next fifty years time travel is invented. A group of scholars in Oxford use this to travel back to earlier eras to witness events. These books focus on a set of said travelers that go to Britain in World War 2.
There is an important aspect of the time travel in that the process itself won't allow travelers to be seen coming or going. If a bystander is around then the 'jump' simply won't open. This means that crowded areas come with a strong challenge. This process also creates a bit of drift in arrival times, sometimes only minutes, sometimes days or weeks. Got all that?
The travelers in Blackout and All Clear soon find that the drift in their time period is very large. They also find that they can't find their way back. Try as they might, they're stuck in London during the Blitz. That means that every night they have to out guess the Nazi bombers. They have some knowledge of what areas get hit but that knowledge is imperfect. Even worse, they get stuck past the time that they studied and soon don't really know where to be.
This is far from a perfect book but the day by day description of what living in a bombing era was wildly compelling. Think of going to work and trying to make it home each day before the bombing started. Each morning you'd wake up and have to try and figure out what had happened to the transportation grid. You'd wonder if your job still existed or if it had been destroyed. You wouldn't know if any of your coworkers, family or friends had been killed. And this happened most every night.
I mentioned that the book has flaws. The biggest of them is the divide between the two volumes. 'All Clear' isn't so much a sequel as a continuation. If you picked it up on its own you'd have no idea whatsoever was happening. These must be read back to back or not at all.
The story that I've heard is that the publisher simply thought that it was too long so they whacked it in half. Willis should have spent more time smoothing out the edges of the halves. And it really is of questionable ethics to push readers to buy two books like this.
Having said that, if you do read it as one piece then it works and works well. The whole thing is something like 1200 pages (not sure of exact numbers since I read it on the Kindle). I read it in about 10 days. Given that all of those days involved two small children and work, well, you can tell that it was compelling. After it was done I wanted to read more. This is about the highest praise that you can give a book.
There have been some complaints about historical accuracy but they strike me as unimportant. The characters aren't the most interesting people but the time period they are in makes up for it. I've been told that Willis hasn't done much different in other books but this being my first reading of hers, I wasn't bothered at all.
The one criticism that I do have is that the nebulous process that governs time travel seemed both too mysterious and too powerful. In this case it let the author do whatever she wanted as she wanted it. This can be ok but it seemed a bit too heavy handed here. The solution wasn't as satisfying as I wanted.
Still, I read it and loved it. I would recommend it to others.