I hear from the grape-vine that this is going to be a really good book! In Eclipes (which I finished reading three months ago) had a girl ( I should say Vampire) that the Cullens wanted to keep. They tried to teach her how to stay by humans without drinking their blood. Until the Volturi came. And that was The Short Second Life of Bree Tanner.
P.S Read the book when it comes out okayyy!