I enjoyed the film and will watch it again. If you haven't seen it and plan to, I'll leave it at that.
I couldn't believe that they basically killed off every character that got introduced in the film though. It gave some additional background to the original films and was entertaining. Of course there's no chance of seeing most of the characters again in any spin off of continued involvement they could've had (if they hadn't been scripted to death) - but it does show potential for about endless possibilities Disney has with the Star Wars universe in that they could make any number of these films to fill a little gap here and there in the overarching Star Wars story everyone knows while standing on its own.
Yes basically it was just a single side story with some small tie ins. So for them to basically all die makes sense, that was they don't have to worry about sequels on it. It was taken from their book series I believe where there are tons of stories all tied in to a massive universe. You are right though, there are enough side story books to make tons of new movies.
So I just got back from seeing this, and I don't know what to say. I am disappointed by it. Doesn't feel like a Star Wars movie at all. Slow and boring. With a few action scenes here and there. To many jokes cracked, to many cute animals, to many things just to sell toys. You can tell it's a Disney movie. It doesn't live up to a Star Wars movie. It just feel like it was created just for kids. Don't waste you time. Maybe a rental only. The original 3 were serious movies. This one felt like a joke.