The novel is in two main parts, firstly Jim's lapse aboard the Patna and his consequent fall, and secondly an adventure story about Jim's rise and the tale's denouement in the fictional country of Patusan, presumed a part of the Indonesian archipelago. The main themes surround young Jim's potential ("he was one of us", says Marlow, the narrator) thus sharpening the drama and tragedy of his fall, his subsequent struggle to redeem himself, and Conrad's further hints that personal character flaws will almost certainly emerge given an appropriate catalyst. Conrad, speaking through his character Stein, called Jim a romantic figure, and indeed Lord Jim is arguably Conrad's most romantic novel.
In addition to the lyricism and beauty of Conrad's descriptive writing, the novel is remarkable for its sophisticated structure. The bulk of the novel is told in the form of a story recited by the character Marlow to a group of listeners, and the conclusion is presented in the form of a letter from Marlow. Within Marlow's narration, other characters also tell their own stories in nested dialogue. Thus, events in the novel are described from several viewpoints, and often out of chronological order.
The reader is left to form an impression of Jim's interior psychological state from these multiple external points of view. Some critics (using deconstruction) contend that this is impossible and that Jim must forever remain an enigma, whereas others argue that there is an absolute reality the reader can perceive and that Jim's actions may be ethically judged.
However, there is an analysis that shows in the novel a fixed pattern of meaning and an implicit unity that Conrad said the novel has. As he wrote to his publisher four days after completing Lord Jim, it is "the development of one situation, only one really, from beginning to end." A metaphysical question pervades the novel and helps unify it: whether the "destructive element" that is the "spirit" of the Universe has intention—and, beyond that, malevolent intention—toward any particular individual or is, instead, indiscriminate, impartial, and indifferent. Depending (as a corollary) on the answer to that question is the degree to which the particular individual can be judged responsible for what he does or does not do; and various responses to the question or its corollary are provided by the several characters and voices in the novel. 
The omniscient narrator of the first part remarks of the trial: "They wanted facts. Facts! They demanded facts from him, as if facts could explain anything!" Ultimately, Jim remains mysterious, as seen through a mist: "that mist in which he loomed interesting if not very big, with floating outlines – a straggler yearning inconsolably for his humble place in the ranks... It is when we try to grapple with another man's intimate need that we perceive how incomprehensible, wavering, and misty are the beings that share with us the sight of the stars and the warmth of the sun." It is only through Marlow's recitation that Jim lives for us – the relationship between the two men incites Marlow to "tell you the story, to try to hand over to you, as it were, its very existence, its reality – the truth disclosed in a moment of illusion."
Postcolonial interpretation of the novel, while not as intensive as that of Heart of Darkness, points to similar themes in the two novels – its protagonist sees himself as part of a 'civilising mission', and the story involves a 'heroic adventure' at the height of the British Empire's hegemony. Conrad's use of a protagonist with a dubious history has been interpreted as an expression of increasing doubts with regard to the Empire's mission; literary critic Elleke Boehmer sees the novel, along with Dr. Jekyll and Mr. Hyde, as part of a growing suspicion that 'a primitive and demoralising other' is present within the governing order.