The world-building here, by the way, is really fascinating. The native culture on the planet is believable while still being very, very alien.
Our point-of-view character is still Dane Thorson, the Apprentice Cargo-Handler and still the youngest guy on the crew. As in the first novel, we see that Dane is still learning. In fact, early on, he makes a serious mistake which only the dumbest of luck turns to the ship's advantage. But Dane is intelligent and willing to learn from his mistakes.
Another parallel to the first novel is that Dane is not the automatic hero--he's a capable member of the crew, but only one member of that crew. Other crewmen contribute to the Queen's success according to their own capabilities and specialties. This continues to be a strength in these stories, creating a sense that the Solar Queen is a real ship that operates in a realistic manner.
At the same time, Dane is given several moments to shine even more so than in the first novel. It's obvious that Andre Norton is still setting him up to one day become a leader of men, taking him through a tough and dangerous learning process in order to get him there.
The crew staves off the efforts of Inter-Solar to muscle in on the trade, but ends up in a situation where they have to carry a cargo to Earth and return within a relatively short period of time. This would have been doable, but soon after they lift off, members of the crew start to get sick and drop like flies.
This is the premise for the bulk of the story. The sickness aboard the ship soon leaves only Dane and three other of the youngest, least experienced crew still on their feet. Whey are they apparently immune? What is the source of the sickness? If it's a plague, they might be banned from landing on any inhabited planet or even forced to fly into a sun.
Why is the ship's cat suddenly terrified of certain sections of the ship? That bit of weirdness is, in fact, one of several clues that help the young crewmen figure out what is going on. (A useful cat? Well, this is a work of fantastic fiction.)
But figuring out the reason for the illness isn't enough. The Solar Queen has been declared a Plague Ship AND (because the Queen grabbed supplies from an Inter-Solar emergency station) a pirate ship. In order to work everything out, the young crew is going to have to hide out in the radioactive ruins left over from an atomic war; kidnap a Medic to treat the sick crew; and commit what could be considered an act of terrorism in order to get their side of the story out to the public.
It's a wild plan worthy of Captain Kirk that leads up to a truly exciting action set-piece.
We're not yet done with the Solar Queen--I'll be reviewing at least one more book in the series eventually.