Wolfling - a novel by Gordon R. Dickson. Serialized in Analog January to March 1969. This is one of Dickson's best books, written when he was coming to the peak of his form - a complete, satisfying tale. I highly recommend it.

Until 10 years before, when their first ship reached Alpha Centauri, the people of Earth hadn't even known that the vast Empire of human-occupied worlds existed. The Princess Afuan of the High-born chose Earthman Jim Keil to return with her to the Throne World, for she'd decided that his performance in the bull ring might amuse the Emperor. What she didn't know was that Jim was a bullfighter only by virtue of 6 month's intensive training, nor that the bull was programmed. Jim Keil was just another Wolfling to Afuan - a lesser being from a backward colony world. Jim was actually an anthropologist trained, mentally and physically, beyond the limits of his profession - his mission was to observe the Throne World and the High-born, and determine whether or not they posed a threat to Earth. One thing that was quickly apparent: the High-born were superior beings - physically taller and stronger than other humans, endowed with faster reflexes, superior mental capacity, and extraordinary technological resources. Their contempt for the new wolfling in their midst was open, their intrigues complex. But Jim Keil knew that if he remained merely a passive observer of the High-born, he'd never survive among them.