I love an epistolary novel, and this one is a killer. A short, gut-punch of a story, written in 1938, about two friends whose relationship unravels as the Nazis rise to power. There's an abrupt shift in the tone and subject of the letters near the end, but the payoff is swift and mighty. I was taken by the story as whole, and even more so by the afterward which posits the idea of "using a letter as a weapon." Chilling and, unfortunately, timely.