Resting in the library

First of all thank you for sharing this piece of art. Secondly I'm not a professional artist so my critique may won't be as useful as it's supposed to be but I will try to give you some feedback that may help you to improve.
Pose is balance, there are some weak points in the way shoulders and neck are joined together though. Nevertheless, it was a good try, there's a correct understanding of that area, but as the position is somehow complicated, you missed the distance between shoulders and the base of the neck. There's a good use proportions but head seems to way bigger compared to the rest of the body, think of the head as half of the chest's width. Respect to colour, I recommend you to use complementary colours instead of using black and white for shades and bights. If you aren't comfortable with tones I would recommend you to do drawings first using black and white and then colour it using layer mode. I would used a darker tone for the shades near the edges to make ensure the image of laying in the floor, in your case shading was too bright, it's almost like he is flying. You've made a great decision with the pose, although there's no point in "resting" some how it transmit the idea that he is laying in the floor for some reason but it feels like wants to interact with the viewer instead of just "rest".
Finally I want to say that this picture has potential. I think it's really sexy and quite impressive. I see a lot of effort in it and I'm sure you will be able of everything if you continue like this. My last advice is to look for some tutorials of over painting and anatomy which are the Achilles' heel of every artist. ٩(ˊᗜˋ*)و