Good book, but the ending doesn't exactly live up to the potential of the story. A great premise! Nice connections with prior episodes and Vanguard that helped create the sense of a larger ongoing 23rd century Trek universe. Good characterization of the regular crew and good interesting guest characters.
I particularly liked how the mystery of Gralafi was solved so quickly. Only about a 150 pages in. I thought there was great promise for a story about this pre-warp civilization given the keys to technology more advanced than the Federation. Would they grow aggressive? Would they eschew Federation assistance to strike out on their own?
Alas, the book does not go that way in favor of a decent cat and mouse game between Kirk and the Romulans in tunnel after tunnel. Unfortunately it felt like the last third was spent doing this. It kind of ground down.
The ending almost came off the like the ending of a pilot novel for another series. Ambassador Sortino was a great guest character and gave off the feeling of a regular character. I think a lot of what I wanted to see was ultimately hinted at as coming up after the novel would end.