The Summer Before the War, which, despite its title, covers the war itself as well as the preceding summer.

Rilla of Ingleside, the last book in the Anne of Green Gables series, is set during WWI, focusing on what life was like for women at home in Canada during the war. It was originally published in 1921, so it's a contemporary depiction. I don't know whether it will be Yuletide-eligible this year, however.