There are a couple other novels here by Timothy Zahn that I’ve summarized and I’ve come away from all of them with the same feeling. Their good but not great, I’m not compelled to stay up late and sacrafice sleep for just a few more pages. There is  enough potential in each book that I’m not willing to give up on either the author or the novel, but…  The Green and the Gray starts with an interesting enough premise and go through a couple twists and turns and ends at a satisfying conclusion. Aliens have inhabited NYC, during the time of immigration through Ellis Island, and have integrated themselves into society. They look more or less like humans and can pass for us. Two different warring factions have come to call the big apple home and until recently each was unaware that the other had relocated. To keep the peace the more powerful greens must sacrafice one of their own, a 12 year old girl, as she has a gift that could literally shake the earth. In the process of her ritualistic sacrafice she is rescued by one unknown faction or another, pushing both sides to the brink of war. As she is rescued however her savior is wounded and has to intrust her care to a pair of passing humans who seem to have the right traits to care for her. The wild ride that the whitteir undertake in caring for her is like nothing the expected and changes both of them in profound ways. All in all this is a good mystery with some sci-fi elements.