Anno Dracula, by I wanna say Kim Newman. There may be another couple of books by a different writer that did something similar, lurking somewhere in my boxes of books I haven't read for years. (Yep, Wikipedia tells me, Anno Dracula and The Bloody Red Baron, by Kim Newman, about what happened when Dracula came to London and Van Helsing & Co. failed to stop him. ETA: I don't recall that vampires outnumbered humans, but it had become a vampire-dominated society.)

I'm really sure there's another book along those lines that I'm not remembering the title of. (Oh, and the original I Am Legend, which I've never read, or even seen the Will Smith movie version of.)