On the recommendation of Ron Rosbottom, I read - and recently completed - Rebecca West's Return of the Soldier, the story of a shell-shocked veteran who returns from the Front convinced that he is in love with a woman he has not seen in fifteen years. This tale of loss, but ultimately of redemption, was quite moving, and reminded me in many ways of E.L. Carr's quiet, and unusually stirring, Month in the Country. I'd suggest both works as (overlooked) masterpieces of the First World War.
From the concluding pages of Return of the Soldier (1918):
"...he would go back to that flooded trench in Flanders, under that sky more full of flying death than clouds..."