The Quiet American is written in Graham Greene's signature style: descriptive but to the point, conversational but tightly structured. He uses long sentences, but breaks them up with hyphens, colons, and semi-colons—keeping the prose rhythmic and moving. Not one to embellish, Greene gives just enough detail to give you a picture. Consider this ghastly scene:
The smoke came from the cars burning in the car-park in front of the national theatre, bits of cars were scattered over the square, and a man without his legs lay twitching at the edge of the ornamental gardens. (220.127.116.11)
A less talented writer might have felt the need to transform this glancing description into a mess of words. You'll notice no adverbs and only two adjectives, used minimally and not in reference to the destruction. Greene captures the scene in all its ugliness with a minimum of words—a style that makes logical sense here as the narrator, Fowler, is looking over the scene in a hurry.
When you're writing fiction, three things—action, form, and content—all have to work together and go together, and this is definitely something Greene understood.