The story is very reflective of Modernism, as are many of Hemingway's other works, such as his first two novels, The Sun Also Rises and A Farewell to Arms.
The structure of the narrative is Modernistic as Hemingway shifts back and forth from the traditional narrative form to the italicized passages that reveal the protagonist's private thoughts and memories. Although the italicized passages are not written in first person or stream of consciousness, they are innovative and effective in exploring the psychology of Harry's inner life, his feelings and memories. Another unusual technique of structure is employed in the story's conclusion as Hemingway moves back and forth between events happening in reality and events happening only in Harry's mind as he approaches death--without distinguishing reality from hallucination.
Two themes common in Modernism are found in the story: alienation and Nihilism. Harry has lived a life of alienation, emotionally distant from his several wives and never identifying with or belonging to the wealthy society in which he has lived, courtesy of his most recent wife's money. As he dies, no spiritual faith sustains him. He has no thoughts of a Supreme Being or an afterlife. He thinks only of all he intended to write but did not write. He worships only the gift he squandered.
Finally, an especially interesting element of Modernism in the story is Hemingway's employment of allusion. Harry's tough and unsympathetic observations about his former friend Julian's destruction is an easily identified reference to F. Scott Fitzgerald, Hemingway's former friend who had suffered a severe emotional breakdown.