by Garth Nix.
Khemri was taken from his parents as an infant, to be raised in isolation as one of the ten million Princes of the galaxy-spanning Empire. As such, his mind and body were augmented; Princes are stronger and faster than ordinary humans, mentally connected to the Imperial Mind, and capable of being reborn in a new adult body if killed in the service of the Empire and judged worthy of continuing to serve the Emperor. Khemri is somewhat shocked to learn that the reason why Princes pretty much have to be tough to kill is that other Princes are constantly scheming to eliminate rivals, to increase their own chances of becoming Emperor; only when officially on duty in one of the six Imperial Services are they more or less safe from murder or challenge, so Khemri joins the Navy. An offer to join a seventh, secret service sends his life in a wholly new and unexpected direction, but the chance of becoming Emperor remains at the back of his mind.
The world building in this teen science fiction novel is pretty amazing. The book is told by Khemri, who takes things like bitek, psitek and mektek for granted and explains very little; and he can't explain much about how the Empire works and what Princes actually do because he doesn't really know it himself. Nevertheless, the structure of the society becomes clear to the reader. Khemri starts out thoroughly self-absorbed and conceited; on becoming a full-fledged Prince at 18, he assumes that of course he will be the next emperor because, really, why else does he even exist? Lessons that come as a shock to him--like the concept that people may not always jump to obey his orders--do start to improve his character.
The book is episodic, and some characters in the first part who look like they're going to be important end up not playing much of a part in later episodes. I enjoyed it, though.
(And it made me want to look up a book I read a long time ago: The Princes of Earth, by Michael Kurland, also a science fiction book for teens. I don't remember it well enough to know how much else it has in common with this one. What I mainly remember about it is some wordplay the main character engages in with his classmates at the University on Mars, which leads them to conclude that he may be worth getting to know better; it revolves around replacing an important word in a phrase with 'tomato.')