Reminds me of Krista from Attack on Titan. Was that intentional?
The linework is crisp and fairly nice, although your values tend to stay in the middle range instead of showing contrasts of light and dark that would really make the piece pop. Anatomically, my only complaint is that the nose looks a little too high, and it then makes the mouth look higher than it perhaps is.
Certainly not bad for a page in a sketchbook. Just remember that each artist may only have one thread in the art gallery section, so if you begin posting other works, it will have to be on this thread.