I like it. Not the best i've read, but i'd definitely give it a B+. I think that you gave enough of a history in the first to give a good background and, while not necessary by any means, a more detailed history would add more to the story.
The plot/story-line seems to be going along pretty good, and i like how harry doesn't seem to be involved with hogwarts in any way so far and is instead choosing to work 'behind the scenes' (which is what the Unspeakables job seems to be).
Good story overall and i hope that you choose to continue it. Feel free to ask me for any help that you need, as i have a fair amount of free time right now.