From time to time, I find myself interested in utopias, dystopias and what-if stories, being not a particular fan, but if the narration is logically developed, then it is catchier than "pure" sci-fi totally based on fantasy.
As ratings here are not so friendly, I had some prior doubts, but alas - the work captivated me from the very beginning and the choice of becoming actors (both English and German, so the German language was used when needed) let the watching smoothly. The era and atmosphere were well taken, the benchmarks of the 1941 events correct (e.g. Soviets and Nazis were rather close until WW II) and the involvement of the US at that time was as it was... True, some moments were odd (e.g. use of public pay phones under dictatorial occupation), the crime itself was soon pushed to the background and the ending could have been wittier, but, in general, SS-GB is a worthy time spending for those interested in both history and crime story.
I suggest to watch this miniseries as an "ordinary" drama, without moral dilemmas or painful spite regarding Nazi symbols in London. Otherwise you will be in the sulks and downgrade its merits...