Clement's world building is the highlight of this sci-fi classic from 1954. Mesklin is a large, disc-shaped world that spins so fast that days are only 18 minutes long. Gravity runs from 3 G at the equator to 700 G at the poles. It is a world of liquid methane seas and ammonia snow. The humans have special environmental suits to protect them from the hostile atmosphere and tanks to get around, provided they stay close to the equator. And yet there's sentient life: 15 inch-long centipede-like beings who are in the early stages of civilization.
And that's the high point of this book.
Characterization is flat. Even the aliens show very little depth, behaving very much like their human counterparts. Interactions between Barlennan, the local Meskinite captain, and Lackland, his human contact, are rather easy. Lackland taught Barlennan English (before the story begins) and except for the occasional idiom or scientific concept, there is little lost in translation. The most interesting part is that the humans and Barlennan's trade group work together to solve problems rather than trying to kill one another.
Science fiction doesn't really age well. Unforeseen technological advances (Computers!) and cultural progression trip up most stories. While the technological hiccups here are few and easy enough to skip over (slide rule, film projector reel), and there isn't any cultural baggage, the writing style is stuck in the time period from when it was written. It's stale. Conversations are all business. The prose is stark, all too objective. It's the Asteroids video game equivalent of literature, with far fewer explosions.
The story is a very linear progression from one encounter to another as the Mesklinites journey from the equator, where they encountered to the south pole of their world to retrieve very expensive equipment from an incapacitated human rocket. It's as much a mission of exploration for the north pole dwelling Barlennan as it is for the visiting humans (though they're keeping an eye on the action via a radio). Unfortunately, we drown in minutiae, both travelogue and mathematical. At times, it seems as if Clement has written this story for boys yearning for careers in science. "Look lads, you can have all sorts of adventures if you study hard!"
It isn't bad, but it isn't terribly exciting either.