The Notebook Trilogy by Agota Kristof

What starts out as a kind of dark fairy tale quickly turns into much more. Twin brothers Claus and Lucas are left to be raised by their grandmother, a more worldly version of the wicked-witch archetype, in the midst of a war that separates them from the rest of their family. They have to adjust to their grandmother’s strange customs, living in a house apart from a nearby village. They have visits from an officer and priest that help expand their worldview and give glimpses of some of the goings on in the world at large. It’s not specified with great detail, but they are surrounded by war and danger and live under this constant threat.