Poul Anderson & Gordon R Dickson 
Star Prince Charlie 
Hoka Book 2

Charlie Stuart, young scion of the Scottish royal family, long nourished a secret desire for adventure – an escape from his dreary books, his sheltered life. When his father realized that, for Charlie to grow into the full Stuart heritage he must face the rigors of the real world, the young man’s dreams had a chance of coming true.But Charlie’s private fantasies had never included Talyina, a planet 200 light-years from earth and ruled by a ruthless usurper. And he had never envisioned himself as a galactic savior. Yet, young Charlie, late the classroom dreamer, suddenly found himself the only man in the galaxy capable of averting inter-planetary war!