This is really busy! The level of detail is extraordinary, and I really admire your patience since I honestly couldn't sit down and spend 25 hours on the same piece. I think I'd go mad. I know it's spread out, but usually if I don't get something done in one sitting it won't get finished. I guess I'm pretty fickle in that respect.
One thing I kind of would like to see is a wider range of values, just to push the foreground forward and the background back, if you know what I mean. With the glass ball being the focal point, I think you could afford to darken the books and such behind the figure in order to make them less obvious, since right now everything in the picture is vying for attention and I think it weakens the composition a bit. Having said that, the glass itself doesn't have any shading at all, which is clever. But I think just a layer of crosshatching over the far background would do a lot to establish some basic planes and really push the idea of the glass ball as the focal point.
Having said that, I don't do much work on paper like this, so I'm not sure I would have the guts to do that myself. I think Photoshop has spoiled me. Also, the thingumajig (I honestly have no idea what it is) in the bottom right corner is fantastic. I want one.
I'm understandably a fan of detail work myself, so I know what you mean. And yes, this was rather time-consuming, although I imagine most people don't realise the amount of time that goes into even my less cluttered pictures.
And thankyou for the +fav. I really appreciate it, and value your support. ^_^