I'd been looking about for this book for ages (since 2011 - see here) but without success. Then recently it popped up for free - or maybe I just found it - on my Kindle Unlimited account; got to be happy with that!
The book starts out in modern Berlin, with an American scholar/author about to announce some shattering revelations about the final days of the Third Reich. He is murdered quite quickly once he begins his announcement and in the course of the investigation the story flashes back to the final days of the Battle of Berlin. Rag tag bands of survivors, German veterans, Volksturm and angry Russians struggle in the ruins of the Reich capital. Then the Vampires made an appearance - shadowy at first and then building to a conclusion with some nice occult bits.
Unfortunately, my impressions of the book were not good. It reads very much like self published fan fiction. Readable (at times barely) and without the style a professional author brings. That said, I persevered and about half way through the book the pace and quality picked up significantly.
Overall I give it 2 stars - mostly because its a Weird WW2 fix and there aren't too many of those about.
PS The author is clearly a fan of Game of Thrones - so don't get too attached to any of the characters!