Robert Penn Warren's style in All the King's Men, through the narrator Jack Burden, is unique in American letters. The narration is full of endless energy, with long, trailing sentences eagerly supplying a variety of images and interpretations to every event in the novel.
Jack's sentences often carry on well past a hundred words. But the style is not wordy or florid—instead Jack is always observant and thoroughly describes the events around him and his own emotions. Jack's narration is not complicated, but it is anything but straightforward, always ready with a simile, metaphor, comparison, digression, or flashback. In addition, Jack rarely makes allusions to literary sources, and in fact rarely quotes from anything. Instead, Jack's memory and imagination drive the book, so the narrative style is always full of small "leaps" to the past that Jack remembers as the story progresses.
The style contrasts with prevailing trends in American writing at the time. Modernism, the predominant literary movement at the time of All the King's Men, was generally characterized by simplicity and austerity in its prose. Robert Penn Warren's breathlessly exuberant style contrasts with other great writers of the era, especially Ernest Hemingway and John Steinbeck, who strove for accuracy through economy of language.
The novel is also noted for its use of American dialect and slang. The novel's dialogue, especially, uses specific voices to distinguish characters from one another. The most distinct instance of this effect is early in the novel at Mason City, when the rural, heavily inflected Louisiana accent of the locals contrasts with the smooth-talking Willie and Jack. In addition to this, throughout the novel, all the characters speak in vigorous, believable dialogue in a style that can be seen as particularly American: blunt, emotional, angry, and hopeful.