Old space opera I loved as a kid. My old copy is taped up. Might have one more read in it. ( )

Not a great book — the best bit is after about three pages, where the protagonist, a young space cadet, is asked by his superior officer to join the Secret Service and he replies, "Secret Service, sir? I didn't know there was one." Anyway, he joins, and starts travelling around the universe using his mind-reading ability to help in securing the release of alien races from servitude or oppression. This book describes his first such mission, involving oppression of telepathic vegetables.