Gulliver's Fugitives by Keith Sharee
While searching for the U.S.S. Huxley, missing for more than 10 years, the Enterprise stumbles across a forgotten colony of humans on a planet called Rampart, where fiction and works of the imagination of any kind are considered a heinous crime. A survey team beams aboard the ship to search for "contraband", and the crew are drawn immediately into a vicious civil war between Rampart's mind police and a band of determined rebels.