A certain trend in YA strikes me as a problem: we too often leave our stories unfinished. In traditionally published books, I've wondered if the publishing company dictated this, cutting a writer's story in two to reduce publication costs and increase sales revenue with the excitement generated by a sequel. We have most certainly seen the movie industry do it to some of our favorites.
One of the many luxuries we DO have as independently published authors is that we DON'T have to do this. There are ways to leave questions open for the next book in the series and yet not leave our readers hanging. In Open Door, I did try to wrap up all the biggest plot questions posed. However, some things that seemed to be mere details will be central problems in the next book. By doing this, I hope to avoid that reader letdown, bad book breakup,"great story, bad ending" feeling.
Here's an interesting essay on the happy ending and the pressure to write one (a bad book breakup from the writer's point of view). I like the point that sometimes the wrong ending can spoil a book--and that it's not fair to your readers to do that. And there's another thing I like about indie publishing: it's the readers who ultimately decide the relevance of what we write to their lives. If what I write doesn't help you in some way (even if that "help" is just a little entertainment), there's no reason you should keep reading. Or buying. There's no go-between here; no one's going to say, "Christine, your readers won't like this! Rewrite it!" And no one is going to say to you, "We decide what's good enough for you to read. Here's a book for someone your age/social class/gender--read it!" You decide what you want to read. I decide what I want to write. The question of whether our interests merge is up to us and no one else. It's brilliant, eh?