A fun romp through a 'classic' hard-SF story: Hal Clement's Mesklin which is a super-massive planet with a surface gravity of 700G at the poles but only 3G at the equator due to its enormous spin that not only elongates the planet but also makes it day last only minutes.

We meet the Mesklin sailor, Barlennan, who negotiates with humans at the equator and agrees to a task in return for aid: to travel to the pole to help retrieve a probe that has refused to take off.

The journey is full of fascinating chemical, physical, biological and psychological thoughts (the Mesklins are scared of heights because of the high G. Even the act of lifting heads is alien to them). And at the end Barlennan 're-negotiates' the deal to achieve a more meaningful goal for his race.

The other major story in this collection is 'Star Light' which is set many years later on another super-massive world. Mesklinites are exploring the world with the help of rovers. But the unique ammonia-water nature of this world would prove to be a major obstacle to exploring it. It also has intrigue as both human and Barlennan try to out-manouver each other while cooperating in the explorating.

And for those who want to know more, there is a final, closing, essay by Clement on how he conceived of Mesklin and thought out their bio-chemisty and physical environment.