Eh, could've been done a bit better. Face looks very off-set and weird. Even a bit mal-formed. Also, shading is a bit weird in two ways. It seems to go in two directions. One direction going pointed up. And the other direction going diagonally down to the left.
Also, shading things is usually a good way to subconsciously tell the viewer, "hey this part isn't important." Which is pretty important to get right when you draw things of erotic value. So shading off most of her ass, just brings attention to her back(which looks good, but not extremely appealing.) and shoulders. Other than that it looks nice. Even though the shading is drawn in two directions, it's drawn well.