Tilly...go down to your Library ( if you still have one ! ) and check out "Fatherland"
Its a fascinating book. It is set on the late 60's and its takes as its premise that Germany successfully brokered a peace deal with Britain, early in the WW2, and America hadn't come into the War. So Hitler and the 3rd Reich are now in power over most of Europe ! But, and I don't want to give too much away, the " Final Solution" took place unopposed but no one knows anything about it...until a German police starts investing a mysterious murder in Berlin.
Its a thriller and very well written...this isn't an "airport" book, if you know what I mean.
I can't recomend it highly enough !