Other reviews are great, very insightful, reading them (after reading the book) adds to the enjoyment of reading the book, for me, giving a chance to think about the issues raised here. The "unnatural" techniques used by both sides of the war require suspension of disbelief, as is always the case with this genre, but the alternate history of WWII in light of this acceptance is very interesting, particularly with the twists and unintended consequences of the decisions made, using poorly controlled unnatural beings on each side. Although the characterizations are spotty, the division of Nazis into evil fiends or cartoonish clods is not a strong point, there is a correspondence with the real history of the time in immoral choices being made by folks on both sides, even in the US (experiments with uninformed soldiers and sailors and civilians to estimate the effects of radiation exposure) and in Japan (experiments with POWs to evaluate biological warfare agents) bringing back to mind the "banality of evil". On the other hand, the drive on the part of many of the Nazi's for recognition, and the resulting infighting and backstabbing corresponds to the historical accounts. Marsh's knee jerk rage in response to threats to his wife and his daughter seem over the top and inconsistent with the intellect that must be present to be such an effective agent, and he and Stephensen's inability to recognize Gretel's ability is also hard to understand if they were really the best of the Brit's counterintelligence agents.