It looks like letter S- Wait a minute...
I think it needs to have the jagged corner of the upper skin just like your cover art
And the color isn't consistent; you know the front underbelly that is dark blue? Try making it light one and the upper skin that is light should be dark.
Try making it like and maybe it could work? Anyways the thing just doesn't look much like the snake on your cover...
Edit: oh yeah, you forgot the snake tongue
I will try to add the jagged underbelly, I'm just always torn on what level of detail makes it look the best, which is especially important in the sudo-minimalist flat art. I will take into consideration the color comment as well, as I mentioned for now the shape is the thing that I want to fix, and then make color corrections, I think I will go with gradient eventually though we will see
The snake is not described in detail in the book (apart from the skin color), so their look changes depending on what I feel like and what I find references for.
Also, according to the handful of pictures of snakes showing their fangs I have, it seems the tongue gets retracted/hidden when baring their fangs.