In "Notes" OBrien recieves a letter from Norman. Why does Obrien choose to include excerpts of this seventeen page letter in the book? what does it accomplish?

This intensive look at Bowker sets him up as a foil for the narrator, O’Brien. There are many doubles in this book: the Vietnamese girl and Kathleen, Jensen and Strunk, Rat Kiley and Jorgenson. In most cases they are each others’ opposites, but are still linked by some sort of commonality. The young Bowker and young O’Brien were on parallel tracks that completely diverged after the war. Only then did the two become opposites: the successful young man and the aimless, damaged vet. O’Brien suggests a remaining similarity, though, by writing about how shaken he was by hearing about Bowker’s experience. O’Brien recognizes that their paths could just as easily have remained the same. This is one of the only stories in the book where O’Brien indicates that he is lucky.