The book's diction, or word choice, is generally quite blunt and to the point. This book doesn't go much for nuance, which isn't necessarily a bad thing. Rand was writing a book about a specific philosophy, so it makes sense that the style would be pretty upfront and blunt… she was trying to educate people about her ideas, after all.
This bluntness crops up in the narrative voice and in the speech patterns of every character. Even shifty characters like Toohey can be pretty upfront about things, as we see at the very end of the second part of the book.
"Mr. Roark, we're alone here. Why don't you tell me what you think of me? In any words you wish. No one will hear us."
"But I don't think of you." (2.15.141-2)
Oh, ouch. We're totally stealing that comeback. Toohey here doesn't seem like a manipulative mastermind, since he just waltzes up to Roark and asks what's up. But again, The Fountainhead's mission is to illuminate a philosophical outlook, not win the Best Screenplay Oscar. Rand's bluntness helps guide even the least engaged readers through the (lack of) emotional turmoil of living as an Objectivist.
Oh, the Majesty
This is a novel about big ideas, and so the style often reflects the novel's dramatic and far-reaching sweep of ideas and events.
She rose above the broad panes of shop windows. The channels of streets grew deeper, sinking. She rose above the marquees of movie theaters, black mats held by spirals of color. Office windows steamed past her, long belts of glass running down... The line of the ocean cut the sky. The ocean mounted as the city descended. She passed the pinnacles of bank buildings. She passed the crowns of courthouses. She rose above the spires of churches.
Then there was only the ocean and the sky and the figure of Howard Roark. (4.20.15-9)
Can't you just hear the music that goes along with that paragraph? The majesty and the symbolism run wild here, as Dominique literally goes up past the past pillars of civilization (religion, finance, etc.) toward a strong individual who represents the future. It's an audacious ending that captures the novel's epic sweep.