I was looking forward to this novel - but I have to say that I found it disappointing.
It was interesting to see Lenore again, only I could have done without her quoting Shakespeare at every turn (reminds me a bit too much of Chang) and her melodrama. I know that's who she was back in Conscience, but it's too much here. And also the notion of rekindling the romance with Kirk. First of all, it's 20 years later, much as happened, both are no longer really the same people, so it just feels very awkward - it would have been better IMO to just talk, instead of immediately implying romantic interest. But I guess, otherwise it wouldn't have made much sense for Kirk to invite her onto the ship. Riley's reaction felt very genuine (as much as Kirk's didn't), on the other hand.
The plot itself... it took ages to gain speed, and I am sorry to say, except for the Enemy Within-twist felt very predictable. It lacked a bit the twists and turns I expect from TrekLit nowadays, especially Chekov's allergic rhinitis practically served the real perpetrator on a silver-platter very early in the game, as does the missing warhead. IMO the story suffers a bit from being stretched out to novel-length. It would have worked well enough in novella-length, especially if you cut the hostage-situation which didn't contribute anything to the overall plot, anyway (except for giving Chekov, Kirk and Chekov's second a chance to stretch their legs).
And there are quite a few things that had me wondering, such as the number of shuttles on board the Enterprise (only 2?!?), why not use the transporters the minute the perpetrator is revealed (there's, after all, only one of the species on board, and the risk is, compared to the risk of her running around on the Enterprise sabotaging everything, quite limited), why not immediately use the shuttle to intercept the warhead (instead of only thinking of it after Lenore escapes with it to surrender herself) etc.
And given Chekov's role in this novel, he should have featured on the cover instead of Spock.
The only convincing parts of this book for me are the characterization of the main cast, which is spot-on, and the little nods to continuity - that kept me reasonably interested and going, and raised my final verdict to "below average".