A vampire from the Twilight world could be a main character. Maybe he's tired of the city life and the constant power struggles among his kind. So he travels to Bear Valley Ranch, attracted by its isolation. And there, he meets a local girl who is not afraid of him and they form an unlikely friendship. There could also be an old wise man on the ranch who has known about the Twilight secrets for a long time and serves as a guide to the others.
I'm afraid I can't tell you the author of 'the last green valley novel'. It could be a relatively unknown author or a new release that hasn't gained wide - spread recognition yet. You may need to do some research, like checking with literary agents or book clubs that focus on new or niche literature.
I'm not sure specifically as I haven't read it in detail. But generally, it might be about a valley that has some sort of unique significance, perhaps related to nature, the environment, or the people living there.