I reviewed this once and closed my browser without saving like a total idiot, and in the face of writing the entire thing again I can feel my brain unspooling from my ears so I'm going to keep it very, very short: 
 1) It is Labyrinth fan fiction. 
 2) No, really. 
 3) The Goblin King has a wild, pale hair, different coloured eyes, sharp teeth, tall, slim etc etc 
 4) Many references to the film. Directly quotes the film (and other fanfics, I'm fairly sure. It all seemed incredibly familiar). 
 5) I didn't like how Labyrinth-y it was. 
 6) I liked the setting of 18th C Germany and the focus on music and composition. 
 7) I didn't like the heroine. 
 8) I really tried but I hated her. I'm sorry. She was so selfish and whiny and her growth was that she accepted herself and acknowledged her faults which is admirable but it didn't mean I liked her any more. 
 9) It is very YA fantasy romance. This may be a good thing or a bad thing for you. 
 10) For me, the ending made the entire thing worth it. 
 11) I'm very surprised there were no characters named Sarah, although maybe she comes later. ;)