While the so-called Modernist movement in literature is generally considered to encompass the early- to mid-20th Century, Joseph Conrad is widely regarded one of the early and major progenitors of that form or style of literature.  Nowhere are the characteristics that define Modernism more prevalent than in his 1899 novel Heart of Darkness.  This tale about a British seaman, Marlow, and his journey on behalf of the Company down the long Congo River into “darkest Africa” to meet up with and bring home his employer’s local representative, Kurtz, represents as well as any novel ever written the bleakness and cynicism that are characteristic of the Modernist movement.  While that movement was reflective primarily of the enormous scale of destruction resulting from two world wars, Conrad’s heritage and observations of the effects of European colonialism provided the optimal prelude to the full-scale emergence of Modernism.  It is no accident that John Milius’ original screenplay for the film that would become Apocalypse Now was inspired by Conrad’s novel.  The war in Vietnam was to Milius (and director Francis Coppola) what the emotional and physical devastation wrought by imperialism was to Conrad and the world wars were to writers like Anthony Burgess and Kurt Vonnegut, the latter considered Post-Modernist, but with a style, in Slaughterhouse Five, that closely mirrors that of his modernist predecessors. 

The experiences of Mr. Kurtz and his gradual descent into madness, along with Marlow’s observations along the way to that fateful encounter, are reflective of the discomforting environments in which much Modernist literature takes place, whether internal, as one would find with Virginia Woolf, or external, as with the following passage from Heart of Darkness:

“I ordered the chain, which we had begun to heave in, to be paid out again. Before it stopped running with a muffled rattle, a cry, a very loud cry, as of infinite desolation, soared slowly in the opaque air. It ceased. A complaining clamour, modulated in savage discords, filled our ears. The sheer unexpectedness of it made my hair stir under my cap. I don't know how it struck the others: to me it seemed as though the mist itself had screamed, so suddenly, and apparently from all sides at once, did this tumultuous and mournful uproar arise. It culminated in a hurried outbreak of almost intolerably excessive shrieking, which stopped short, leaving us stiffened in a variety of silly attitudes, and obstinately listening to the nearly as appalling and excessive silence.”

This is not Gothic literature, with its convergence of horror and romance.  Nor is it horror, per se, despite Kurtz’s now famous lamentation before his final breath, “The horror.  The horror.”  It is simply a bleak, violent, despairing indictment of Western policies and the corrosive effects of those policies on the souls of those dispatched into the darkest corners of the world to enforce.  Marlowe and Kurtz are both the quintessential alienated figures, emotionally as well as geographically distant from the worlds that created them.   If the nihilism in Burgess’s A Clockwork Orange represents the external manifestation of Modernist expression, Virginia Woolf’s Mrs. Dalloway represents the more internal emotional dysfunction characteristic of this movement:

“Selling gloves was her job. She had her own sorrows quite separate, 'and now can never mourn, can never mourn,' the words ran in her head. 'From the contagion of the world's slow stain,' thought Clarissa holding her arm stiff, for there are moments when it seems utterly futile (the glove was drawn off leaving her arm flecked with powder)--simply one doesn't believe, thought Clarissa, any more in God.” [“Mrs. Dalloway in Bond Street,” engl201buscemi.wikispaces.umb.edu/.../Mrs+Dalloway+in+Bond+Street...]

Topics characteristic of Modernism vary widely.  Subject matter in-and-of-itself is not the point.  Style, tone and atmosphere are the characteristics of Modernism, and they can and have been applied across a wide range of topics.  The cynicism, bleakness, alienation and sometimes surrealistic approach to a subject are all more important than the topic.