I forgot how to do spoiler code and my previous post was a spoiler mess, but......
In the book - the vampires seem to be able to turn someone after death.
Henry helps hunt down JWB, (a vampire) and then turns Abe.
The whole setup of the book is Henry approaching an author in modern times and getting him to write the story of Abe (all of it).
The book was a good little read that for me rarely dragged.