Man of Many Minds, by E. Everett Evans - [from the first-page blurb]: GALAXY IN DANGER! Somewhere, somehow, the first moves have been made - the pattern is beginning to emerge. Someone - or something - is on the way to supreme power over all the planets held by Man. And the Interstellar Corps is helpless to meet the threat - no normal man can hope to penetrate the conspiracy. But - the Corps has a man who isn't normal, a man with a very strange weapon... his mind.
[the back-cover copy]: "You're a disgrace to the Corps!" Hanlon cringed at the Admiral's icy stare. "You had a good record, Hanlon - a fine future in the Interstellar Corps. Now you thrown it away. There's no room in the Corps for a cheat!" Hanlon blustered, "I didn't- you have no right-" "That'll do!" Disgust showed on the Admiral's face as he gestured to the Marines, who grabbed Hanlon's arms and handcuffed him. "George Hanlon, you are hereby dismissed from the Interstellar Corps' Cadet School!" And the Admiral ripped the identifying symbols from Hanlon's uniform. "Take him out of my sight!" They hauled Hanlon away, disgraced... But inside, he was jubilant. Now his real job of counter-intelligence would begin!
[This has a sequel which has never appeared in paperback: Alien Minds.]