This is the second book in the "Space Trilogy" that began in Out of the Silent Planet. I've seen the titles on several science fiction recommendation lists, and the books are considered classics of the genre, but if you've read the first two books, it's evident that what Lewis wrote was consciously un-science fiction. That's not simply because of the liberties taken with science--pretty much all science-fiction writers do that. Einstein's theory of Relativity tells us nothing can exceed the speed of light, and our science tells us any inhabitable planets are years and years away at that top speed, but it doesn't stop such contrivances as "hyper-drive" and "warp drive."
Nor is it so much that this isn't so much fiction about science and technology as it is Christian allegory. Early on in Out of the Silent Planet I thought it obvious these books have much more in common with Milton or Swift than Verne or Wells. That's only underlined in this novel which is basically a Paradise Lost set on Venus, with the "Green Lady" as an unfallen Eve and Weston from the previous novel in the role of the serpent--and it's very Miltonian in the way he attempts to subvert her. But then all great science fiction has its underlying message. You can't read Isaac Asimov's Naked Sun or Robert Heinlein's The Moon is a Harsh Mistress or even Scott Westerfeld's Specials without being aware of a message, even if it's much more blatant in Lewis.
Part of Lewis' message though is against the humanistic thrust of science fiction itself. In the last book, Ransom spoke of the purpose of the book as "a change-over from the conception of Space to the conception of Heaven." This book talks of the very idea and dream of space exploration, particularly as envisioned in science fiction, as opening "a new chapter of misery for the universe." There's an anti-Reason and anti-science streak in Lewis--and Christianity--I've always found unattractive very evident here. And at times I found his Christian polemic eye-rolling. Especially early on when one absurdity of the doctrine of bodily resurrection is pointed out to Ransom and he counters with this idea of the "trans-sexual." (Admittedly, a lot of the giggle-worhiness of the moment comes from a contemporary meaning of the term Lewis could not have anticipated.) I see Ransom's arguments as much as a sophistry as those of Weston. (Much of Weston's cant is strikingly contemporary--when he rants against "dualism", I can't help but think of a friend's tirade against "binaries.") Like another reviewer though, I did find it disconcerting that Lewis--or at least Ransom--feels violence is a great resolution to a conflict when you're losing an argument. In other words, for all that so many have pointed me to him as a Christian apologist with a brain who would appeal to an intellectual, I don't find Lewis convincing.
So why did I keep reading anyway despite all I found dreary, unappealing and unconvincing? Well, partly because I do want to read the conclusion, That Hideous Strength, because I hear it deals with Arthurian legend. But there's also that I have no doubt when I'm reading him that Lewis is a first rate writer with a first rate mind. He's a pleasure to read, despite his didacticism. And you know, I've seen Lewis accused of racism and sexism in Narnia. I thought that a bum rap even while reading Narnia for several reasons, but it's only cemented in my mind that's wrongheaded reading these two books. The first book stands as a great refutation and repudiation of racism and imperialism to my mind, and the books stand out to me as the anti-thesis of xenophobia, with imaginative alien worlds that stand very much in contrast to more paranoid scenarios of alien beings. It's evident--and all the more resonant knowing the first book was published in 1938 and this one in 1944--that Lewis very much does not believe color or shape matters. Lewis might be an Englishman and in many ways conservative--that doesn't make him a Kipling. And while I can see a patriarchal thrust to the "Green Lady" and her King... Well, admittedly, I might not feel that way if I hadn't read Paradise Lost recently and noted all the ways Milton ground the very idea of Eve being an equal into dust... but in contrast Lewis doesn't come across as misogynistic to me given this book is practically, Paradise Retained, Or Milton Fan Fiction.
So, yes, a superbly written and at times thought-provoking (even if at times hair-pulling) book worth the reading, even if it lacks the charm of the Narnia books. And a short, fast paced read too.