I have nearly finished the lower half of the figure. The large smooth areas like these legs are a little tricky to render, especially when you are working from photographs. If you didn't carefully look at the subtle value shifts, you could end up with the surface that is not too convincing about its 3-dimensionality. Observing subtle value shifts on the surface of the human body and trying to make sense of them is an intellectual game like solving a puzzle. It gives me a chance to recall what I learned about how all the bones and muscles are connected, and to imagine what they are doing under the skin in this particular situation I am drawing.
I think this drawing is compositionally complex and interesting. It has a semi-bird's eye view of the model. The surface she is lying on is basically a flat tabletop, and yet there is an illusion of exaggerated spatial depth created by the conversing edges of the fabric. Then the perception of the space is optically further distorted by the use of a wide angle lens in shooting. The back edge of the table neatly cuts the picture plane at the 1/3 from the top, creating a flat space in the background that doesn't seem to belong to the rest of the picture and stops our expected spatial perception of the typical one-point perspective. There is a nuanced interplay between flatness and three dimensionality, which, come to think of it, is a recurring visual game I have played many times throughout my work in various mediums.