You'll notice the influence of "A Sound of Thunder" on this blog, and my thoughts: the sign that we read in the beginning is not the same one we read in the end, and it is because of the actions of the reader.
I'm struck by the way his opening sentence shows us what we need to know. I'm struck by the rhythm he uses in the short paragraph that starts, "First a day and then a night and then a day and then a night," suggesting what it might be like to time travel. I'm struck by a later sentence that communicates, in its syntactical repetition, the complication of the subject of time and influence: "Eckels glanced across the vast office at a mass and tangle, a snaking and humming of wires and steel boxes, at an aurora that flickered now orange, now silver, now blue." Finally, I'm struck by the fact that in this story, Bradbury takes us first into the future and then into the past, showing how our choices affect our world. It's thunderous, a matter of life and death.