Chris Bachelder makes as good a case for Upton Sinclair's The Jungle as I've read in a while:
The Jungle aims to provide an accurate report of the many ways that life in Packingtown crushes people, destroys their power of self-determination, even their humanness. Individual desire, typically the engine of fiction, is eradicated. If Sinclair’s characters seem to lack agency or a certain kind of Rooseveltian pluck, if they seem unresponsive or passionless, well, that’s the point. Readers may long for a tender conversation between Jurgis and Ona as they hold each other on a particularly cold night, but as Sinclair writes, “truly it was hard, in such a life, to keep any sentiment alive.”
Later in his career, Sinclair knew himself well enough as an artist to tell the critic Van Wyck Brooks that “some novelists I know collect their material with a microscope, and I collect mine with a telescope.” E.L. Doctorow once said that contemporary American writers are more technically proficient and far less socially or politically motivated than previous generations of writers (many of whom began as journalists). Readers of contemporary literary fiction have grown accustomed to the novel’s microscopic power to render, often beautifully, the small moments of a character’s life. Conversely, we’ve grown skeptical of the novel’s telescopic function to bring large, distant abstractions into focus. We’re wary of the big picture. And if the accurate depiction or explanation of the world outside our minds is not a part of our conception of Good Literature, we will fail to recognize the power of The Jungle.
The problem with this, however, is that an "accurate depiction" is not the same thing as an "explanation." A realist writer (Flaubert or James, for example) may indeed render an accurate depiction, either of the world inside or outside our minds, without presuming to offer an explanation--an ideological or conceptual grid onto which we are to project the depicted world. More often than not, through the focus on the concrete rather than the abstract, such writers ultimately convey more of the complexity of human experience than its capacity to be reduced to simple explanations. In effect, the more we know, the less we know. (In this sense, the epistemic skepticism Bachelder speaks of in his essay is a consequence of the novel's own "artful" techniques of exploring experience rather than the "sustained attacks on objectivity and truth" by contemporary philosophers.)
Sinclair pretty obviously did want to provide an "explanation." He wanted not merely to portray "the many ways that life in Packingtown crushes people," but to bring the reader, along with The Jungle's protagonist, to an appreciation of socialism as an alternative to the unrestrained capitalism the novel exposes. And, as Baldechar pouts out, Sinclair himself admitted he had failed at this goal: “I aimed at the public’s heart, and by accident I hit it in the stomach.” Still, sickening readers through the power of description is not an insignificant accomplishment. It does show that whatever skills as a writer Sinclair did possess finally overshadowed his more dubious talents as a political theorist.
Although one can acknowledge the "power" of The Jungle and still wonder why it needed to be written as a novel at all (beyond the usual bromides about the way novels offer "identification" and "intimacy"). The accuracy of its depictions could have been achieved just as readily in nonfiction as fiction, their truthfulness perhaps becoming only more consequential as a result. Is "accuracy of depiction" even something that distinguishes fiction as a literary form in the first place?