Devil World

Summary
From the back cover: Voyage to Heartland

Heartland... a mysterious planet populated by a small but terrifying race of demonic beings.

Heartland... where Captain Kirk falls in love with a beautiful, mysterious woman with a fatal secret.

Heartland... where Kirk, Spock and the rest of the Enterprise crew will be challenged by an awesome disembodied intelligence, more powerful than any other force in the universe!