"Mission of Gravity" by Hal Clement (1954)

"...but Mesklin was not even approximately spherical.  As Lackland had long ago recognized, the proportions of the Bowl on the Bree - Barlennan's equivalent of a terrestrial globe - were approximately right."

Hal Clement spent most of life teaching high school Astronomy and Chemistry.  Mission of Gravity is his best known book, and although he wrote throughout his teaching career his more recent books are much less familiar to the sci-fi reading public.

Mission of Gravity is an adventure story similar to Larry Niven's Ringworld.  A human astronaut visits a supermassive, oblate world, and has to rescue a lost probe with the help of alien traders.

Like Ringworld, the characters in Mission of Gravity are pretty hard, if not impossible to relate to.  They're little more than plot devices, but fortunately for them the plot's fairly interesting and their personalities are somewhat beside the point.  The most fleshed-out character is the leader of the alien traders, but his quirks regarding things like being picked up or falling down don't always add up to a picture of who - or what - he is.

If you've read Ringworld you can probably guess the overall shape of the plot.  Characters start at point A and try to get to point B, but then stuff happens, and they have to figure out ways of overcoming obstacles.  Ringworld adds a slight twist to this time-tested formula in that some of its characters are at cross-purposes, and their conflict adds an extra dimension to the story.

This said, Clement's oblate world could be an actual, physical reality, whereas Niven's Ringworld is pure fantasy.  Both books are grouped within the "hard science fiction" category, but Niven never quite bothered to think through all the implications of a ring-shaped world.  His introducing certain "modifications" in The Ringworld Engineers was, moreover, worse than not addressing the issues in the first book at all.

But hey, if you're looking for a well-known science fiction novel to read, you could do worse than either book.  Ringworld offers a better story, while Mission of Gravity is a more thorough example of worldbuilding.  Both books were very important to the development of the genre, and a familiarity with either won't take up too much of your time.

Related Entries:

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"The Martian" by Andy Wier (2011)
"Arrival" by Ted Chiang (2015)
"Make Way for the Super Humans" by Michael Bess (2015)