..."Willie McCoy had been a jerk before he died. His being dead didn't changed that." does a much better job of what I think this author is trying to do.

I don't believe that example does "a much better job" of what Elliot James actually did in his prelude. The only thing established by those words is how Anita Blake thinks of Willie McCoy. They don't even establish whether or not there is magic in that world, since they say nothing about how Willie McCoy is still being a jerk while he's dead. It could just be a real world detective story where he's still being a jerk through his will or some other aspect of how people can continue to be jerks after they're dead. Elliot James actually established the presence of magic in his universe, and that knowledge of magic is limited in his universe.