First off, I'd like to say that you created for me a goal that I want to reach. Thank you for that.
The shading and lighting is absolutely phenomenal, and the moon was an excellent touch.
I also love the contrast in the shading of the ghost woman. The highlights give off the feeling that she's glowing, yet at the same time the shaded parts keep her grounded in the material plain. All the while, the transparent parts and the surrounding aura are handled very well.
The ghost's highlights also contrast well with the man and the rest of the environment, as they are dimly lit in most areas. It really makes her pop out even more.
You obviously know what you're doing, man. Keep up the great work.