Another good one is 'Birdsong' by Sebastian Faulks. It weaves together the story of a man in the present day researching his family's past in World War I with the actual events during the war. It has some very poignant and memorable scenes of life in the trenches.
For a more comprehensive view of the war's impact on society, 'Testament of Youth' by Vera Brittain is a must - read. It's a memoir - style novel that shows the experiences of a young woman during the war, from her work as a nurse to her personal losses.
Sure. 'Regeneration' by Pat Barker is excellent. It focuses on the psychological effects of war on soldiers and is set in a military hospital. Barker does a great job of exploring the trauma and the attempts at recovery.