The original question had to be edited down. I think that one way in which Hamid is able to construct an atmosphere of tension for the reader exists in the relationship between the American and Changez. Hamid does not make clear whether the American is there innocently or if he is there to actually do harm to Changez. Since the reader does not know the American's capacity, the entire narrative structure of the novel is one where tension exists. Details are given to the reader. Yet, these details are obscure enough that they can be understood in any particular manner. The "shiny" object at the end of the story is the most compelling of all of the details. Hamid leaves enough to speculate widely about the presence of the American and his relationship to Changez.
At some level, this speculation is reflective of what the reader feels about the presence of fundamentalism or terrorism in the modern setting. This makes the reader almost a part of the novel. As it becomes evident that Changez undergoes his own sense of change about his beliefs, the reader has to undergo the same level of self- examination about their own beliefs regarding the American and his presence in the novel. It also becomes clear that the reader has to evaluate Changez at the end of the novel. Whether or not Changez means to do harm or rather simply speaks in an elusive way to bring out the prejudice that he believes is at the heart of the modern war on terror are elements that remain unclear. It is almost as if the reader is put in the same limiting paradox that all of the characters are immersed in as a result of the attacks of September 11. If one is predisposed to see terrorism as a real threat, than there is a likelihood that the reader will see Changez as a terrorist and the American as almost an "avenging angel" to put this threat down. If one sees the limitations on the "war on terror," there is confusion as to whether is a threat or whether he needs to be suppressed in the first place. It is here in which there is tension evident, something only added by the fact that the perception of the reader is almost as much a part of the novel in constructing this. It is here in which the reader becomes a part of the novel, helping to develop this atmospheric element of tension and uncertainty.