Great idea, but the execution leaves some things to be desired. I like how radically alien the cheela are—physically, not mentally/socially—with their reconfigurable bodies and difficulty moving north/south. But the plot and characters are not particularly compelling.

The cheela operate on a dramatically faster timescale than humans (who they call “slow ones”). This is interesting, but I’m not totally happy with the story’s treatment of it. There’s an underlying assumption, common especially in older sci-fi like this, that civilizations naturally progress through a fixed sequence of stages. And a sense that perhaps there’s something inherently good about that journey. So as the cheela progress beyond us technologically, they leave us to our own devices. Contact between the two civilizations is an anomaly, a brief point of intersection before they continue on their separate journeys. Contrast that with a more recent entry in the watch-a-civilization-develop genre, Children of Time.

Avoid the audio version; the narration is very stilted.