I'm with Ian. I enjoyed this one a lot. Nothing "earth-shattering" but I gave it an "above average."
It was entertaining, breezy, not particularly deep. A good 5-year mission romp. And I always enjoy the Horta.
I wondered about Nahrat too. I sort of imagined he was in there somewhere, and this was how some of the Horta (including him) ended up in Starfleet.
It reminded me of the old numbered novels: fun, exciting, a quick read, a little shallow. But, that's exactly the kind of story I was in the mood for so that's okay. I love the deeper, weightier novels we've tended to get lately but they don't ALL have to be that way.