There have been lots of interesting suggestions, a number of which I wouldn't mind seeing myself.
I'll add two more to the the list, although maybe a little obscure to get an RPG treatment.
The Cycle of Fire - Janny Wurts
The Wars of Light and Shadow - Janny Wurts
She co-wrote the Empire novels with Ray Feist. Her world building, I think, is second to none and some very interesting dynamics that she creates within those worlds.
I'll add two more to the the list, although maybe a little obscure to get an RPG treatment.
The Cycle of Fire - Janny Wurts
The Wars of Light and Shadow - Janny Wurts
She co-wrote the Empire novels with Ray Feist. Her world building, I think, is second to none and some very interesting dynamics that she creates within those worlds.