What were the effects of 1st world war on English literature?

World War I had a tremendous effect on English literature. The war itself become the subject of some very good poetry by soldiers such as Siegfried Sassoon and Wilfred Owen; their poems were usually more innovative in subject matter (e.g. devasted landscapes or poison gas attacks) than they were innovative in structure. Structural innovation, however, dominates the high-brow literature from the emerging writers in the years just after the First World War. The modernist techniques in literature were already developing before the war began, but they found their greatest expression just a few years after the war ended. I think that multiple elements tied to WWI -- such as shell shock and battle-scarred landscapes -- inspired writers who were already interested in exploring the psychology and shattered worlds of their characters.

The single most important study of the impact of the First World War on English literature is probably still Paul Fussell's book-length work The Great War and Modern Memory (1975, 2000). It's written in a very accessible and gives extensive discussions and concrete examples.