I just finished reading All Clear and Blackout, a two-volume novel from Connie Willis’s Oxford Time Travel series. I also read Firewatch and The Doomsday Book, which are earlier stories in the series.
All Clear and Blackout are about three time traveling historians from the future who get stuck in England during World War II. The writing is brilliant, the historical information in the books really teach you and make you want to learn more about World War II, and you feel completely engrossed in the story. I found myself looking up information on the Internet, watching WWII movies, and checking out WWII books from the library. I found WWII timelines and Eyewitness books to be especially helpful.