The Joy Machine (Star Trek, Book 80)

Plot

Timshel was once the vacation spot of the galaxy, full of culture, natural beauty and friendly, hospitable inhabitants. But now Timshel has cut itself off from the universe; no one is allowed to enter or leave. Concerned, the Federation has sent agents to investigate, but none have returned. Then Captain Kirk and his crew discover the truth--the people of Timshel have succumbed to an insidious new technology that guarantees every citizen total pleasure.