The Moon is Down by John Steinbeck
I love John Steinbeck. You probably know this. If not, you can read about it here and here and here and here. I've already read The Moon is Down, but I went back to read it again.
Written in 1942, The Moon is Down is essentially a social commentary on war. While nothing is too explicitly said, the occupying forces are obviously German, and the seized town lies somewhere along the upper Western coast of Europe.
It is one of his shorter books, and the characters aren't nearly developed as Steinbeck characters tend to be. But, I see that more as way to focus on the commentary instead of characters. Instead, Steinbeck aims to show the civility in war, the second guessing by occupying forces, the ability to question authority, and what happens to a people when faced with injustice. It's very simple, but the interplay between the occupying authorities and their soldiers is, I believe, the most interesting.
I loved re-reading the book, especially because at the end I came across a quote I remembered, which I believe says a lot about the theme of the book. It is stated by Mayor Orden, at the end of the book, realizing that he will be put to death by the enemy.
"You know, Doctor, I am a little man and this is a little town, but there must be a spark in little men that can burst into flame. I am afraid, I am terribly afraid, and I thought of all the things I might do to save my own life, and then that went away, and sometimes now I feel a kind of exultation, as though I were bigger and better than I am..."