Geez, Kim Newman: what took you so long?
This is the latest in Newman’s alternate… literary history, I suppose: imagine Bram Stoker’s Dracula, only the Count wins and goes on to transform the British Empire. At least, for a while. The series is pretty much a paean to the vampire genre, with liberal importation of every other book that Kim Newman likes, and Newman has excellent taste in literature. Start with Anno Dracula itself and just keep going would be my recommendation.