I read this short novel around 2014, in the UK, in English. The cover was dark pink or red, and the title was something that smelled like a ripoff of the Da Vinci Code.
One of the main (viewpoint) characters was an assistant of John Dee, I think named Edward or Edmund. He was married, but loved Dee's wife; at some point in the story, a succubus appeared to him in the form of Dee's wife. He and Dee were travelling together in mainland Europe, I think visiting a Polish king?
The main antagonist was a Hungarian noblewoman who became a vampire. I think her name was Elizabeth or Erszebet (the Hungarian form of Elizabeth).
If I remember rightly, the story followed two parallel timelines, one in the sixteenth century with Dee and his assistant, another in the modern day. I can't remember any of the modern characters (I think there was a small team of protagonists), but the ancient vampire woman was a common antagonist in both storylines.
Not many details, but hopefully distinctive enough to identify the story? I searched a bit online, trying search terms involving Dee and Elizabeth/Erszebet, but mostly found historical pages about Dee and his queen Elizabeth I. It's not The Alchemist's Door at least.