It's a nice idea to keep the title in German, but not practical when the bulk of the market will be in America, Canada and the UK.
How about "Himmler's Sacred Order" with a subtitle "An illustrated guide to Der Totenkopfring der SS"
It pretty much sums up the book, keeps the Germanic aspects intact, but also does not undermine the importance these rings had to both the men who earned them, and Himmler himself.
