Star Trek: A Flag Full of Stars

Faz 18 messes que a Enterprise completou sua missão de 5 anos e sua lendária tripulação se separou, recebendo novas missões que se espalham por toda a galáxia. |...| [Star Trek: The Original Series #54] It has been eighteen months since the Starship Enterprise completed her historic five-year mission and her legendary crew has seperated, taking new assignments that span the galaxy.

On Earth, Admiral James T. Kirk has married and started a new life as the Chief of Starfleet operations where he is overseeing the refit of his beloved ship, now commanded by a new Captain -- Willard Decker. Kirk's only tie to his former crewmates is his Chief of Staff, a young Lieutenant Commander named Kevin Riley.

But Kirk's new, quiet life changes when he meets a scientist named G'dath who is on the brink of perhaps the greatest scientific discovery in a century. G'dath's invention could mean tremendous strides in Federation technology, or -- in the wrong hands -- the subjugation of countless worlds.

When Klingon agents capture this new technology, Admiral Kirk and Lt. Commander Riley are all that stands between peace and devastation for the entire Federation. |...| [From Memory Alpha: the Star Trek Wiki]: As part of the Lost Years saga, this story takes place between Star Trek: The Original Series and Star Trek: The Motion Picture.
The novel explains some of the refit procedures that turned the Original Series Enterprise into the one seen in the feature films. One of the major overhauls was that the saucer section was removed and landed on Earth where it was rebuilt and then launched back into space.