I thought I had read this before - I rated it - but none of it sounded familiar, except inasmuch as the style of magic detailed is rather similar to that of the Adept and the Hunting Circle. It's a very rich, rather dark story of occultists (their choice of neutral word) working to save Britain during WWII, in the world of Kurtz's Adept. Hitler's black magicians, and Hitler himself, are the opposition; on Britain's side is everyone from Freemasons to witches to Druids. Our heroes are trying to get them all to work together, to block the German invasion that's clearly in preparation. Prince William gets involved, with the authority of being of the sacred line of kings - and the duties and consequences of his choices that follow. Solid characters, very rich story on many levels. In an afterword, she mentions that nothing she invented conflicts with the historical record - there are several points where her characters are only speculating, and of course their own actions are not in any record - but there are records of a good many events that are described or referenced in the book. Good, rich, glad I read it, but I don't like it quite as much as I do the Adept books. I'm pleased it's been re-released as an ebook, from Open Road Media - I got a copy from them in return for a review (when it was released, in 2016), but I also owned the paper book from an earlier release.