During a mission to an outlaw planet, Kirk is killed by the collapse of a burning building. Spock suspects that the situation was engineered--murder. His suspicions are confirmed by Omne, the leader of the planet, who offers him a clone of Kirk--a perfect clone, in body and mind--in exchange for his cooperation in a plot to set the Federation and the Romulan Empire against one another. Then the Romulan Empire will ally itself with Omne's planet in a war against the Federation, thus--Omne claims--safeguarding galactic freedom which is being stifled by the expansion of the Federation.
Omne's ally in this is none other than the (unnamed) Romulan Commander from The Enterprise Incident, though she rapidly turns to Spock's side, and is unaccountably taken with Kirk, as well.
It transpires that the original Kirk is still alive, and the balance of the book is occupied by Spock, the Commander, and the clone (who Spock calls 'James', in contrast to the original 'Jim') making their way though Omne's underground complex to reach Kirk, with both the group of rescuers and Kirk periodically having violent confrontations with Omne. The larger threat is that Omne's technology which enables effective immortality will allow him to control the galaxy.
Ultimately, Omne is killed during a fight with Spock, and the four are able to escape. He is resurrected, and again killed during a final confrontation on the Enterprise, and it is left unclear whether he will be able to return again. The clone, James, is made up to look like a Romulan, and will leave with the Commander. The two will work from within the Romulan Empire, as Kirk and Spock will work from within the Federation, to ensure an eventual alliance between the two powers.
This book (and its sequel, The Fate of the Phoenix) are polished-up versions of a privately published fan novel, Never Mourn Black Omne, and its origin shows. It is very slashy, and filled with (what must be) the authors' preoccupation with dominance, masculinity, and sadism.
The writing is poor, with highly repetitive descriptions--all muscles are 'corded', the connection between Spock and James is always 'gossamer', etc. The characters, all from different planets, show a remarkable unity of though, all conceiving of men as being 'alpha males' or 'wolves', considering negotiations in terms of poker, and on and on. One cannot help but feel they are all mouthpieces for the authors.
The characterization, too, is far off. One could just about see Kirk surrendering himself to save Spock, but the despairing, weak-willed creature we see cannot be our captain. Spock, too, can be self-sacrificing, but the impulsive, emotional wreck in these pages is no Vulcan. And at last we have the Romulan Commander. Her, we know little about, but even so, her behavior is inexplicable, as she praises Kirk and Spock (the former especially) as the greatest men in the galaxy, and seems to desire nothing more than to be with them. Inexplicable, unless she is serving as a stand-in for the authors, and, by implication, the readers. Omne, too, shows very thinly-veiled attraction to Kirk, and seems willing to abandon his current plans in exchange for having Kirk as his permanent companion and slave.
The authors had one or two interesting ideas about the impact of the federation, and what life would be for the clone, but they do not explore them, devoting the text instead to fetishization of physical strength and violence.
I've seen a few reviews that dispute my claims about the slashiness of the book and its focus on sadism, but I think a few selections from the text will suffice to prove my point.
When Omne brings Spock to the clone of Kirk, who is sleeping naked beneath a nearly-transparent sheet, he says:
And shortly after:
Later, Omne and the original Kirk fight one another, and the following exchanges occur:
There is nothing strictly explicit in the book, but the subtext is clear.
The authors claim, in Shatner: Where No Man... that Shatner thought that this should have been the script for the Trek film:
And they reiterate that claim in Voyages of Imagination: The Star Trek Fiction Companion:
It's hard to believe that this event could have occurred at all, and nearly impossible to imagine that it was anything but flattery by Shatner. But maybe in some alternate universe, the Trek movie series turned into ten or a dozen BDSM-themed angst-fests, and started the Fifty Shades revolution a few decades early. There but for the grace of god...