Writing in the age of Impressionism, Conrad showed himself in many of his works a prose poet of the highest order: thus, for instance, in the evocative Patna and courtroom scenes of Lord Jim; in the "melancholy-mad elephant" and gunboat scenes of Heart of Darkness; in the doubled protagonists of The Secret Sharer; and in the verbal and conceptual resonances of Nostromo and The Nigger of the 'Narcissus'. The singularity of the universe depicted in Conrad's novels, consists of creating a sense of place, be it aboard ship or in a remote village. Often he chose hat his characters play out their destinies in isolated or confined circumstances. In the view of important literary critics, like Evelyn Waugh and Kingsley Amis, it’s surprising that only in the 50s, another English novelist achieved the same command of atmosphere and precision of language with consistency, (Anthony Powell’s A dance to the Music of Time) a view supported by present-day critics like A. N. Wilson. This is more remarkable, if we think that English was Conrad's third language. Powell acknowledged his debt to Conrad.

Conrad's third language remained under the influence of his first two — Polish and French. This makes his English unusual. It was perhaps from Polish and French prose styles that he adopted a fondness for triple parallelism, especially in his early works ("all that mysterious life of the wilderness that stirs in the forest, in the jungles, in the hearts of wild men"), as well as for rhetorical abstraction ("It was the stillness of an implacable force brooding over an inscrutable intention").

T.E. Lawrence, one of many writers who were Conrad’s friends, offered some perceptive observations about Conrad's writing:

He's absolutely the most haunting thing in prose that ever was: I wish I knew how every paragraph he writes (... they are all paragraphs: he seldom writes a single sentence...) goes on sounding in waves, like the note of a tenor bell, after it stops. It's not built in the rhythm of ordinary prose, but on something existing only in his head, and as he can never say what it is he wants to say, all his things end in a kind of hunger, a suggestion of something he can't say or do or think.... He's as much a giant of the subjective as Kipling is of the objective.

In Conrad's time, literary critics, while usually commenting favorably on his works, often remarked that his exotic style, complex narration, profound themes and pessimistic ideas put many readers off. But Conrad's ideas unfortunately came to reality  by 20th-century events, so these times seem closer to him than his own.

Conrad had a lucid view of the human condition and the fight between Good and Evil inside the human’s heart — a vision similar to that which had his ten-years-older Polish compatriot, Bolesław Prus (whose work Conrad admired) in his micro-stories: "Mold of the Earth" (1884) and "Shades" (1885). Conrad wrote:

“Faith is a myth and beliefs shift like mists on the shore; thoughts vanish; words, once pronounced, die; and the memory of yesterday is as shadowy as the hope of to-morrow....

In this world — as I have known it — we are made to suffer without the shadow of a reason, of a cause or of guilt....

There is no morality, no knowledge and no hope; there is only the consciousness of ourselves which drives us about a world that... is always but a vain and floating appearance....

A moment, a twinkling of an eye and nothing remains — but a clot of mud, of cold mud, of dead mud cast into black space, rolling around an extinguished sun. Nothing. Neither thought, nor sound, nor soul. Nothing.”