The agents
To Slahi, the American intelligence agents represent agents of death and torture. They abduct him without explaining their reasoning, and before he knows it, he is being tortured for information he doesn't have. The agents symbolize the US government, and the invasion that Slahi considered it to be approached at his home and extradited without charges to a foreign government. In a broader sense, they represent the paranoia that defined American politics following the 9/11 terrorist attacks.
Torture
Through painfully explicit motif, the reader is asked to judge for themselves the torture that Slahi endured. For American readers, the motif comes with a painful judgment against social acceptance of such practices (because many did historically support torture—many still do). These tactics represent a human rights violation, because he was treated this way by a government without respect to the human rights legislation from the UN.
The absence of due process
The very laws that define American freedom are denied to Slahi who is assumed to be an Al Qaida member without due process. He isn't charged by the US government for any crimes, and he is given no trial. The punishment he is faced with is severely cruel and unusual, and it isn't even punishment; it is an attempt to extort him of information that he doesn't have. The absence of due process is an astonishing fact.
The symbolic ending
Although Slahi is freed later, the book is finished from his cell in Guantanamo Bay where he was still being kept without formal charges, in complete isolation, still subject to serious mistreatment. After the book's publications, he is freed, but he spent fourteen years in that high-security prison for terrorists. There was never a trial to officially tie him to any crimes, but the US government still kept him.
Censorship
Perhaps the most outrageous aspect of the book is that it was published with censorship. The US government only allows the book to be printed in a redacted form, so that much of Slahi's story is literally obscured by black ink bands that disallow the reader from knowing the truth about what they did to him. This censorship symbolizes something that is almost too frightening to consider.
