Informative; Detail-Oriented (and "Hippopotamus-Like")
Let's put it this way: some readers have not been fans of Dreiser's style. One famous critic even accused him of "writing like a hippopotamus." (Source.) We're not exactly sure what that's supposed to mean, but hippopotamuses aren't known for their lightness or grace.
Some kinder readers have simply chalked up Dreier's straightforward, unpoetic style to his background in newspaper reporting and writing. And indeed, many passages in the novel are chock full of facts and thick with detail, the way a newspaper article might be:
The firm of Speigelheim & Co., makers of boys' caps, occupied one floor of the building, fifty feet in width and some eighty feet in depth. It was a place rather dingily lighted, the darkest portions having incandescent lights, filled with machines and work benches. (3.57)
Dreiser's writing style certainly helps to paint a clear picture (even if it's not a Monet).