Blackout and All Clear by Connie Willis

Connie Willis' Black and All Clear are closely tied together. From what I understand they started out as one book and had to be split into two. So you may want to read them fairly close together. They are sequels to The Doomsday Book and To Say Nothing of the Dog.

Blackout and All Clear are set during WW II with three main characters. Mike who is "studying" heroes by visiting Dunkirk and the rescue there, Polly who is studying the shelters and the way people behaved in them during the Blitz (lucky her, she knows when and where the bombs will fall.) And Eileen who, on her 1st mission, is studying the evacuated children. Poor Eileen has the worst cover.  She is working as a house maid in the country with numerous evacuated kids.

Most of the books' story takes place during WW II and I found it very interesting. I learned a lot about how regular people lived and how they lived through the Blitz.

There was a lot I didn't know about the Blitz. For example, I knew about ration books and that people had to go to bomb shelters but I didn't know that they had "subways" and that's where a lot of people went before the sirens even went off, with their blankets and picnic baskets. I also didn't realize that there were different types of bombs dropped, including unmanned rockets toward the end.

The lengths the military went to to plant false information was astonishing to me. I knew about removing the street signs but blow-up tanks with fake tracks - that I didn't know.

The time travel aspect is an important part of the story. The preparations they had to make before traveling were really quite extensive, from learning to drive an ambulance to an implant to give Mike an American accent.

I've always been a fan of Time Travel books and these two certainly didn't disappoint me.