Most Trek books get a pretty standard 3-star rating. Not great, not bad, but good mindless escapism. This is one of the few to drop below that. Very poor characterizations for most of the main characters, a clumsy story with too many things going on, and some very odd and occasionally uncomfortable scenes (the discussion between Kirk and Lorelei in her quarters, with it's repeated instances of "the pose would be sexual if she didn't look so much like a child," culminating in Kirk starting to come on to her, just ends up being icky).

A decent bit of social satire, but you have to slog through quite a bit of racism, classism, sexism, and colonialism to get to it. More dated than I'd expected from an early-1960s book, it felt more akin to late-1800s literature in its assumptions and style. Still worth reading if you're at all curious, as long as you keep that in mind.