In a superficial sense, his book is thorough; he quotes from a variety of different people to make his points. However, because the vast majority of his sources are merely defending policies which they implemented, his apologetic comes across as self-serving. Asking Dick Cheney whether or not waterboarding is meritorious is akin to asking Joe Biden whether the stimulus program worked. We know what we will be told, but we remain unsure as to the real answer.
Theissen offers a cursory defense of the morality of enhanced interrogation techniques, to wit, it's not torture, and anyway, there are different rules when dealing with terrorists. Yet the thrust of his argument is utilitarian: "We should be grateful to, and proud of, those who took on the difficult job of interrogating captured terrorists. They elicited information that saved countless innocent lives."
The danger of his approach should be obvious: if safety becomes the only test of morality, it is difficult to see which of our rights are inviolable. That some of our freedoms remain is beside the point: once this test has been admitted, there is no logical reason why government may not strip away our rights—one by one.
There is a greater flaw in Theissen's book, however. Until the very last chapter, he does not so much as examine why it is that terrorists may be attacking America. Then, he flippantly insinuates that terrorists are simply evil. He quotes Peter Rester, the director of the Joint Intelligence Group at Guantanamo, who notes that critics cite: "America's support for Israel; America's occupation of the Holy Land; America's occupation of Saudi Arabia" as policies which give impetus to terrorism against the United States. But for Theissen, discussions about policies are excuses, irrelevant to the discussion.
Nothing could be further from the truth. Theissen insists that if the terrorists attack again, the Obama administration will have blood on its hands, since the attacks could have been prevented had we continued to use enhanced interrogation techniques. Yet it is truer to say that American policies—indiscriminately bombing Middle Eastern countries, insistence on occupying these same countries, and unquestioning support for Israel against the Palestinians—produce what our CIA calls blowback. Terrorists attack us because of these policies; we know this because they have told us as much. This does not excuse the behavior of those who kill innocents, but it does make it partially explicable.
This does not necessarily mean we need to reverse our policies. But we need to accept that there are costs for our Empire—just as there are costs for refusing to utilize enhanced interrogation. A prerequisite to Theissen's book is an understanding of our foreign policy, and the role it plays in fomenting terrorism. It is puzzling that he considers something so essential to be of so little consequence.