When I finished this book, I picked up another to read, and just couldn't do it. The "message" in this book is really strong and it takes a bit to digest. Even better, I don't think there is a single message. This short book was written brilliantly, so you can see whatever you want in the relationships.
This story takes place in some future or alternate timeline. Through whatever means, there are aliens living on earth. Emshwiller did a fantastic job describing, not so much what they look like (she did use some descriptors, but except for some fuzzy descriptions, you are left entirely to your own devices to imagine what you would like) as their relationships with and actions towards humans, who have (through, again, whatever means that is not described) become their "mounts" or servants.
I loved that Emshwiller did not bother with details about how they came to Earth, how long ago they did it or how it is they have actually tamed and selectively bred the human species. Clearly, it must have been generations, because the characters in the story were unaware of a lot of these details, and many people have been bred into distinct lines (Seattles, Tennessees). I've read a lot of books slamming her for leaving out these details, but I think it's not the focus, or even remotely important to the book.
This specific story is mostly about a young adolescent named Charley, who has been selected because of his superb breeding and conformation to be the mount for the next ruler. They both start off young to be trained to be the best mount and rider they can be. Charley is rescued by his father, Heron, and is taken to a village in the mountains where Heron is leading be beginnings of a revolution of people, which Charley objects to, but cannot fight. Eventually Charley and the future ruler of all get back to "civilization", changed and in a changed world and begin something new.
This novel lands itself squarely in the "speculative fiction" arena, and it's not so much fantasy or sci-fi, and anyone looking for fantasy/scifi will be very disappointed. The writing is as tight and fantastic as any I have read in a VERY long time. The story isn't plot driven and there is plenty of plot to keep anyone from getting bored. It's about characters and relationships, and this author has packed more relationships into a short book than most could put into an entire series, and the psychology in this book is amazing.
The themes of this book are strong, and consistent: slave/master relationships, slavery and individualism, adolescence and "finding" ones-self, and the struggle between parent and child. Reading the book, I kept thinking of the brainwashing/raising that Charley went through, and how it reminds me of the justifications and Stockholm Syndrome-like behavior of victims who always justify their abusers. Charlie is a pre-teen/early teenager in the book, and he does go through conflicting emotions, thought processes, and behaviors, which might seem inconsistent, but I read it as a conflicted and confusing boy trying to rationalize what was going on and find his place with what little he had to work with.
My biggest quibble with a book is the immensely unrealistic ending, but it's not terrible, it was just a little unbelievable, even though it did leave some questions and unresolved issues.
I really wish Goodreads had a half star system, because I think this book is stronger than four stars, but not quite five stars. Because I really did find it amazing and interesting, I figured I would push it to five stars.