This novel represents an advance in Said's thinking from his initial work Orientalism, which is a text prized by postcolonialists. I will highlight some of the main ideas, but obviously reading through it yourself is what is most important.
Said identifies a series of assumptions that are made by the West about the Orient. Said himself is Palestinian, and he identifies a series of assumptions that the West makes about Arabs: they are irrational, anti-Western, menacing and dishonest. He explores how these assumptions are constructed in opposition to what the West thinks about themselves, and therefore defines this projected image of "Arabs" in the mind of Westerners as the other - we define the other by what we are not. The danger is that these assumptions come to be treated as truth and therefore impact our relations and our ideologies.
Said therefore calls for a new treatment of "the Orient" - allowing for self-representation of authors belonging to the Orient rather than depending on second hand representation. He also objects to half the globe being labelled "the Orient" - you can hardly make generalisations that will apply equally to Eqyptians as you can to the Chinese, for example. Tell any British person that they are just part of the United States of America, and you will probably receive a black eye!
Above all, Said helps us explore the processes of constructing binary opposites and uncovering the values that cause these opposites to come into being. By doing so, he calls for an erasure between these boundaries and lines that we construct and a more moderate way of thinking. If you want some examples of these binary opposites and how they are applied to the West and to "the Orient", think about these oppositions and how they are used: civilised / uncivilised, democracy / despotism, developed / undeveloped, liberated / repressed, educated / ignorant. You might want to look back at American foreign policy and judge how many decisions have been made from the standpoint of "us" having the answers and making decisions on the part of "them" who are ignorant and therefore do not know what is best for them.