Good review; several points:

- I think Tolkien probably was highly embarrassed by the Ransom-as-Christ syndrome you get by the end of the third book, and I suspect was also pretty mortified by the sort of things that Lewis had Ransom saying by that point. It sort-of-kind-of makes sense that Lewis would do that, since it was Tolkien who converted Lewis to Christianity; as such, it's understandable that Lewis would be massively grateful to him and consider him at least partially responsible for his salvation. I believe there's letters where JRR says to CS "dude, chill out, you're taking this whole Christ thing a bit far".

- I personally really disliked That Hideous Strength, mainly because of the misogyny but also because the plot is just plain weaker. I also get what you mean about the vindictiveness; I honestly don't think it's a problem in Perelandra, where it's focused more-or-less exclusively on a single villain, and also (I seem to remember) comes across more as the natural consequences of the man's shittiness finally catching up with him. It is a problem for me in That Hideous Strength, for all the reasons you describe.

- I think the second book is far and away the best, mainly for the horror sequences, which are fabulous (not many people can make me afraid of a goat in a railway cart, but Lewis can) and because if you can see past the preaching (which really isn't too bad in this series until you get to That Hideous Strength) poses a question which s actually a legitimate poser for secular and religious authorities alike: what if human expansion and colonisation of space is a fundamentally bad thing, akin to European colonisation wrecking societies across the globe back in the day? I think part of the reason the Space Trilogy is considered so important is that up until that point next-to-all SF had an overwhelmingly optimistic view of space colonisation, so Lewis presented an interesting discordant voice at the time.

- Lastly: have you read A Voyage to Arcturus by David Lindsay? (You can still find the Fantasy Masterworks reprint if you hunt about.) It's the book Lewis read which inspired the Space Trilogy, mainly because he found it so disturbing that he felt he had to write a response to it: it's a decidedly non-Christian allegory, lacks the preachiness that Lewis can't quite suppress, and is a million times trippier than the most out-there segments of the trilogy. I think it blows Out of the Silent Planet and sequels out of the water.

Thanks! I agree that the disturbing stuff in Perelandra is considerably less awful than the stuff in Hideous Strength... but I will still quite troubled by the description of what's-his-name being beaten and then chased and then begging for mercy and then being killed (by Ransom with his bare hands) and then killed again... I think that these scenes give the novel some power and the villain (whatever his name was) certainly deserved some of it... but it still felt pretty icky to me. Maybe it's just the brutality of the... physical stuff that's involved in actually killing someone with your hands that got to me.

I didn't know anything about the place of the Space trilogy in the history of SF when I read it, but I'm impressed that Lewis was the first to consider the possibility that there was a downside to conquering the universe... he's certainly more serious in the way he thinks about the philosophical consequences of humanity expanding out over everything in sight than just about any other sf author I've read. But I'm not an sf expert, by any means. :)

...speaking of which, no, I haven't read "A Voyage to Arcturus". It sounds like the kind of thing I would enjoy... I'll keep an eye out for it.

Just to clarify, I don't know whether Lewis was the first SF writer to suggest negative consequences of human expansion into the universe at large, but he was certainly amongst the first to do so at a time when the majority opinion was overwhelmingly positive.