Code Name Verity by Elizabeth Wein is the best book I’ve read in a very long time. The problem is, I don’t want to say much about it because it’s best read without any hint of how clever, how loyal, how absolutely strong two people can be. I can’t even tell you the names of the characters because figuring it out is part of the plot.
What I can say is this: Two friends discover how deep comradeship flows when they are separated yet still allied against the evils of the Nazi regime. Strong women who can fly planes, talk in code and search for verity.
If you need more, you can read this article. (But I highly recommend reading the book first).