Illyria won the World Fantasy Award for best novella back in 2008, when it was published in the UK. Now, I have nothing to do with the World Fantasy Award (which is probably a good thing considering my general apathy for the genre), but looking at some of the other winners, this one doesn't quite seem to fit.
Madeline and Rogan think of themselves as two halves of the same soul. Children of identical twins who share a birthday themselves, they are inseparable as children - an intense friendship that grows into an intense love as they enter their teen years.
Multiple generations of their large family all live on the same block, all descended from a great stage actress, though Madeline and Rogan are the only ones who have retained a love of theatre and performing, encouraged by their great aunt who appreciates the art of theatre, though doesn't seem to perform herself.
When cast as the stars of Twelfth Night in a school production (Madeline as Viola, Rogan as Feste), Madeline and Rogan must begin to confront their separate talents and where they might lead them, even as their relationship grows in intensity in the face of adversity.
Notice how in that description there isn't much that would really fall into a "fantasy" story? It's more like what one of my college professors called magical realism. This is a rather straightforward story about two extraordinarily close cousins who face some adversity because of their peculiar talents and relationship. The fantasy/magical element comes from an apparently enchanted miniature theatre they find embedded in the walls of the attic, where the lovers escape for their illicit trysts.