Harder to rate on a 2nd reading – I recall really liking it before, so I’ve probably added a + to make up for the fact it wasn’t novel for me (particularly having between the two readings enjoyed The First Men in the Moon, and so becoming aware of Lewis acknowledged debt to Wells). I mean, it has a lot more thought going than your standard SF novel and a fabulously grand historical cosmic setting (although the characters are fairly one dimensional – almost personifications of certain viewpoints), and the fact I was expecting this undermined my pleasure.
People (and aliens) are defined the way Lewis defines them: morally. Other attributes are secondary.
There’s the Lovecraftian sense of non-anthrocentrism, although each planet’s species has a benign angelic overseer – except humanity. From this come all our ills, particularly illustrated in this story, greed and humanism. The former is dismissed cursorily, the latter more carefully undermined, challenging the notion that technological advances bestow rightful authority (a far less popular idea since 1945).
As a wonderful idea to explore an argument and a world view, this is admirable. Look elsewhere for action sequences, snappy dialogue, and psychology: Lewis’ characters consistently, purely and rationally act out their basic convictions.
(2nd Reading – 1st in early 1980s?)