STAR TREK : TIME FOR YESTERDAY by A. C. Crispin, Paperback Novel, 1st UK Edition 1988. Published by Titan Books Ltd.
 
A brand new unread copy in NM condition.
 
Time in the galaxy has stopped running in its normal course. That can mean only one thing - the Guardian of Forever is malfunctioning. To save the universe, Star Fleet Command reunites three of its most legendary figures ; Admiral Jmes T. Kirk, Spock of Vulcan, and Dr. Leonard McCoy and sends them on a desparate mission to contact the Guardian, a journey that ultimately takes them 5,000 years into the past. They must find Spock's son Zar once again and bring him back to their time to telepathically communicate with the Guardian.
But Zar is enmeshed in troubles of his own, and soon Kirk, Spock and McCoy find themselves in a desparate struggle to save both their world - and his!