World of Ptavvs (The Tales of Known Space Series‪)‬

Nothing quite prepared telepath Larry Greenberg for mind-to-mind contact with an alien. In the interest of science, Larry tapped the mind of Kzanol—and that was his first mistake.

Kzanol was a thrint from a distant galaxy. He had been trapped on Earth in a time-stasis field for two billion years. Now he was on the loose, and Larry knew everything he was thinking. Thrints lived to plunder and enslave lesser planets—and the planet Kzanol had in mind was Earth!