Where to start?

So I'm obsessed with vampires, like much of the free world seems lately, and I decided to write a book.  At the risk of jumping on the vampire bandwagon I came up with this story that I don't think anyone else is doing or has done.  From what I've read (and I've read too much) the two main 'mythologies' used in writing vampires is the supernatural mythology, where they're undead, magical creatures, or the disease mythology, where is a blood disease that twists the genetic make-up of the host and so explains all the cool powers in something that somewhat resembles science.  Sort of like science fiction, it can be close enough to nearly be plausible so it becomes more believable.  Well, I'm all about believable, so i decided to take it a step further.

I'm all about sexy too, which, to me, the modern vampire should be.  The true myth, whether its the spirit feeding on human spirits or the walking corpse, isn't always sexy.  Rotting walking bloated corpses with seeping gases and drips of blood at the corners of their mouths have a long way to go to reach sexy.  But Dracula, he was sexy.  Hell, he's still sexy, and its been over a hundred years.  That's what I want.  I wanted more of that.  Believable and sexy - with still enough mystery to be fantasy.  Because if its not fantasy, what's the point?  So I wrote a story I wanted to read - and I hope others will too.