Cast No Shadow (spoilers)
The Star Trek movies introduced two new characters who played an important role in a movie or two then seemingly faded away, despite the need for new characters and new relationships to keep things fresh. The first, Saavik, has had some exploration in a handful of novels and issues of the early 1980s DC Star Trek comics, but I can't help but think she deserved a lot more. Still, she's done much better than her fellow Vulcan, Valeris.
Valeris's part in Star Trek VI was originally written with Saavik in mind. I'm glad that didn't happen. Not only did that leave Saavik as an uncorrupted character who could be expected to continue playing a role in the series, it introduced a new character with a new and intriguing relationship with Spock. Granted, her part in the criminal conspiracy meant that she could hardly continue as a regular member of the crew, but it still seems strange that it should take twenty years before we'd get a book that explores her character.
But finally we have James Swallow's new novel, Cast No Shadow. It answers some of the questions and leaves others unanswered, but more importantly it does so in the form of a suspenseful espionage novel. A few years after the events of The Undiscovered Country, a terrorist attack in the Klingon Empire is revealed to have connections to the conspiracy that killed Gorkon and tried to prevent peace between Federation and Empire. And the best clue a young Starfleet Intelligence analyst named Elias Vaughn leads to a convict: Valeris.
Though Spock is prominent on the cover, he's not a main character. Vaughn (from the DS9 relaunch and other books) and Valeris are the main characters here, but there are a number of other interesting characters along the way, including operatives from a number of secretive organizations. But this is a rite of passage for Vaughn and a tale of possible redemption for Valeris, and some other characters aren't as fully developed as they could have been, including the terrorist group. For that matter, we don't get Valeris's own thoughts at some key points in the plot, which keeps up the level of suspense -- can she be trusted? What does she want? Why did she do what she did, and why is she doing what she's doing now? Swallow ultimately provides believable answers, though the Spock/Valeris connection is not explored in as much depth as the cover might lead a reader to expect.
Speaking of the terrorists... Swallow uses the Kriosians, whose canonical appearances I'd pretty much forgotten about. Turns out there's some dispute over whether the various Kriosians seen in Enterprise and two episodes of The Next Generation were all meant to be from the same civilization. My official Star Trek iPad app says no, other sources say yes, and Swallow goes with the latter. As always, he works in a lot of nods to continuity in unobtrusive ways.
The book avoids the obvious cliches. Valeris doesn't suddenly realize she was wrong then put everything right by sacrificing herself in some noble and fatal way. Vaughn doesn't instantly become the Federation's best field agent. Though the terrorists' final attack is obviously going to be averted somehow, because we know from 24th century Trek that the Klingon homeworld wasn't destroyed and the Klingon Empire didn't fall, how everything is going to play out is never predictable.
(I could call them freedom fighters instead of terrorists, but Swallow presents them as a relatively callous and unsympathetic bunch, as eager to kill Federation citizens as Klingons. That's arguably a weakness, as is the characterization of the individual Kriosians; they tend to the one-dimensional. Even with the importance of Federation/Klingon detente, I'd expect a bit more sympathy for the position the Klingon-occupied Kriosians are in from Starfleet officers.)
Overall, it's another solidly entertaining standalone novel. But I wouldn't mind another Valeris story with a bit more Spock in it. And more Saavik novels, dammit, with the Kirstie Alley Saavik.