A Green and Ancient Light

Young G——(only one character's name is spelled out), sent from the city to his grandmother's rural/small town home during a long war, explores the nearby forest and finds a garden of monsters.

This is a quiet, slow-paced coming-of-age fantasy, about the boundaries of Faerie and mortality. It evokes WWII, but it's not explicit, and some of the details suggest otherwise, and while soldiers play a distinct role in the plot, they're not the focus. I'd class this as a low fantasy rather than high, more concerned with the effect of magic and faerie than their nature; readers who enjoy Robin McKinley might check this out.