hey man ! nice work, the shading looks good. For the anatomy, you almost get it. To learn to draw perfect anatomy, you should buy a burne hogart book or check in google. This guy drew characters with perfect anatomy and I learned where are the muscles by checking his art. good luck man !
Nice job, it looks really good. You could do better though. I would like to see how it looks when you finish it up. When you finish the final touches to it, i will add this to my favorites. Keep it up, the anatomy shows well, but can be brushed up. I'm inspired, i'll keep working hard on my work too.