I have spent a couple of good days reading Radiant Green Star, which got both a Hugo and Nebula nomination in 2001. It's a great pleasure to read a story so well-constructed, with just enough twist in it to make it interesting and not confusing. The story is set as a struggle among wealthy and powerful people, but in the modest circumstance of a traveling circus, and Shepard spends a lot of time in the inner life of our protagonist, a half-American Vietnamese boy named Phillip.
I feel a need to be mildly critical as this seems to me to be a good story that could have been really good. It's just a bit long for what it accomplishes--might have been filled out further for a novel, or cut to a novelette. His most striking side character is The Major, the last American POW, who has had horrible genetic experiments carried out on him that have granted long life and weird disfigurement. And while he is carefully woven into the story and has important moments, in the end I couldn't figure out his true place. The speculative part is a backdrop to the emotions and circumstances of the protagonist, which can make for a good tale and in this case does. I give it 3 stars, and you would not be sorry if you spent some time reading it too.