In "The Lake of the Woods," O'Brien does not employ chronological narrative; Why? How does the structure support the themes of the text?
There are many reasons, but here is the one that I think is the most important. Many modern novels do no present life in an orderly chronological sequence because that's not the way it happens. The past, specifically John Wade's, is always there in his present life, influencing his relationship with his wife on one level (private), and finally ending his public life. His narrative reminds us of this because the past is introduced into the story in the same "disorderly" fashion in which it intrudes into his life.
On another level, this is the way we get to meet people in "real" life. We never get to follow the progression of a person's life. Rather, we find out bits and pieces about his/her past, personality, deeds, etc. We wonder about John when we first meet him in the fog at the lake; as we read on, his past emerges, as it were, out of the fog event by event, recollection by recollection, evidence by evidence.
This is also a great way to maintain interest and curiosity about the characters. The evidence chapters (not chronological, just randomly introduced), do much the same as they offer possibilites and take them away, returning us to our speculation.
I wonder what "The Scarlet Letter" would be like had Hawthorne written it this way?