Finished it last night.
Some highlights:
The new "alien" race - the Dinac.
Introducing new species must be a real challenge for an author, particularly when he or she is writing a tie-in novel and thus must focus on the marketable characters instead of devoting 50 or 60 pages to the history and biology of the new species. Mr. Swallow did a fine job giving a brief outline of the race, and some interesting glimpses into their culture, history, and technology. Bonus: Wooden starships!
Characterization:
The characters all felt accurate and authentic, and nothing happened during the course of the story that felt out of sync or "smelled wrong." Although I still find that William Riker is one of the most boring Trek characters ever created - Mr. Swallow did a good job of working him through the trials and tribulations of being in command but not in command, and the struggle of making command choices when those whom he loved were in mortal danger or perhaps even dead.
The final sacrifice of one of my favorite new TrekLit characters was heartwrenching, but very well written, as was that character's funeral/wake. Serving in Starfleet is an immensely hazardous job, and I liked how Mr. Swallow did not shy from using an established character to make the sacrifice, rather than use the standard "guest actor we get to know a little through the episode bites it in the end".
The villians
Wow. What a nasty bunch of evil they were. They had been featured in one of the creepiest episodes of TNG, and they lived up to their reputation. Anyone catch the fact that they kept looking for "The Solution"? I wonder if it was the "Final Solution." Creepy, chilling, vicious, and thoroughly evil. Well done.
I get the feeling that the Federation will have to deal with them again in the not-to-distant future.
I really couldn't find anything to complain about above a subjective nit-picky level, and I am looking forward to Mr. Swallow's next Trek novel.