The 20th century was like no time period before it. Einstein, Darwin, Freud and Marx were just some of the thinkers who profoundly changed Western culture. These changes took distinct shape in the literature of the 20th century. Modernism, a movement that was a radical break from 19th century Victorianism, led to postmodernism, which emphasized self-consciousness and pop art. While 20th century literature is a diverse field covering a variety of genres, there are common characteristics that changed literature forever.
Prior to the 20th century, literature tended to be structured in linear, chronological order. Twentieth century writers experimented with other kinds of structures. Virginia Woolf, for instance, wrote novels whose main plot was often "interrupted" by individual characters' memories, resulting in a disorienting experience for the reader. Ford Madox Ford's classic "The Good Soldier" plays with chronology, jumping back and forth between time periods. Many of these writers aimed to imitate the feeling of how time is truly experienced subjectively.
If there's one thing readers could count on before the 20th century, it was the reliability of an objective narrator in fiction. Modernist and postmodern writers, however, believed that this did a disservice to the reliability of stories in general. The 20th century saw the birth of the ironic narrator, who could not be trusted with the facts of narrative. Nick Carraway, narrator of Fitzgerald's "The Great Gatsby," for example, tells the story with a bias toward the novel's titular character. In an extreme case of fragmented perspective, Faulkner's "As I Lay Dying" switches narrators between each chapter.
The Novel of the City
The 20th century is distinguished as the century of urbanism. As more people moved to cities in Europe and America, novelists used urban environments as backdrops for the stories they told. Perhaps the best known of these is James Joyce's "Dubliners," a series of short stories that all take place in various locales in Dublin. Other 20th century writers are also closely associated with various urban centers: Woolf and London, Theodore Dreiser and Chicago, Paul Auster and New York, Michael Ondaatje and Toronto.
Writing from the Margins
The 20th century gave voice to marginalized people who previously got little recognition for their literary contributions. The Harlem Renaissance, for example, brought together African-Americans living in New York to form a powerful literary movement. Writers such as Langston Hughes, Nella Larsen and Zora Neale Hurston wrote fiction and poetry that celebrated black identity. Similarly, female writers gained recognition through novels that chronicled their own experience. Finally, the post-colonial literary movement was born, with writers such as Chinua Achebe writing stories on behalf of subjugated peoples who had experienced colonization by Western powers.