Vlad the Impaler, or Dracula.
Judging from the blurb on the back and the selected reviews, it seems to be aimed at people who enjoy books about vampires and I've seen more than once the suggestion that it is an update of Bram Stoker's Dracula. It isn't.
I will confess that I found my attention wandering at times and in part this was due to finding it hard to tell who was the narrator. There are three narrators: the daughter who remains nameless throughout, her father, Paul, and her father's mentor, Professor Bartholomew Rossi. They all sounded much the same. I have to say, the narrative wandered a bit and there were many times when I wondered how much of the history/geography was fact or fiction.
However this was more than compensated by the wonderful, atmospheric, descriptions of Eastern Europe and Turkey. In many ways this is padding to the plot and I can appreciate there is rather a lot of it but it may be what saved an overly long novel as far as I'm concerned.