I finally finished this book last night. I really enjoyed it. It was written in 1982 so well before the Fire and Ice Series (Games of thrones books).
It's about a man, Abner Marsh, who is a steamboat captain and owner on the Mississippi River in 1857. He is having money problems and meets a man, Joshua York, who wants to build a new ship with him but with some "rules".
Joshua is a vampire but different from all the other vampires in fiction today. Check out this book and you will really enjoy it.