One of the first things I noticed when reading the book was the style in which it is written, especially the sentence structure. A lot of the sentences seem to go on and on. For example, the sentence on page 14 that begins "They plodded along slowly, dumbly..." is almost an entire paragraph in and of itself. The very thing it is describing--walking endlessly, trudging mindlessly, on and on--is reinforced by the way that sentence is written. It marches on and on and gives the reader a definite sense of an endless repetition of the same actions, the same words. It is very effective at conveying the desired feeling, I thought, and O'Brien uses that tactic a lot throughout the story.
He uses it as well when describing the things the soldiers were actually carrying. Those were some of my favorite parts, when he says "They carried chess sets, basketballs...diseases...infections. They carried the land itself." The way he lists everything, so many things, in a seemingly never-ending paragraph is a very effective way of conveying the magnitude of how much those boys had to carry, both physically and emotionally. I think that writing style definitely adds to the story; I like that aspect a lot.
O'Brien also writes very haphazardly as far as timeline and plot are considered; he seems to write things as they occur to him instead of in a logical order. But he makes a statement on pg 34 that explains that very well: "What sticks to memory, often, are those odd little fragments that have no beginning and no end." I loved that line because it's so true. People don't remember situations exactly the way they actually occurred. They remember them in bits and pieces, and sometimes the most seemingly insignificant occurrences are the ones people remember for years. I thought that was a good way to explain why O'Brien writes these seemingly insignificant anecdotes in a random way; it helps illustrate the way human memory works and how people tell stories about their experiences later on.