Lost Years, The (Star Trek) by J.M. Dillard - Vintage Paperback

Recounts the adventures of the crew of the Enterprise after they completed their original five-year mission, detailing how Kirk, McCoy, and Spock managed to enter into as much danger as they did when they were in space. Captain Kirk, Mr. Spock, and Dr. McCoy struggle to establish new lives apart from each other and the starship.

The newly-promoted Admiral Kirk is placed in charge of a specially-created Starfleet division and attempts to defuse a critical hostage situation; Mr. Spock, who, in the midst of a teaching assignment on Vulcan, finds the one thing he least expected; and Dr. McCoy, whose unerring instinct for trouble lands him smack in the middle of an incident that could trigger an interstellar bloodbath.