C. S. Lewis is said to have found "Perelandra" his favourite among his own books, and an improvement over "Out of the Silent Planet". Though a strong Lewis fan, I'm afraid I cannot agree. OOSP attempts one thing, and achieves it perfectly. Perelandra fails by being too ambitious.
"Out of the Silent Planet" is an almost perfect story. The description of Martian creatures and scenery is delightful, without the author having to ram home how terribly significant it all is; and the evil targeted for attack is limited, believable, and allowed to collapse under its own weight. (Ransom's translation of Weston's speech out of the Shavian-evolutionary into Malacandrian i.e. plain English is one of the funniest things I've read.) In Perelandra, on the other hand, the author is always TELLING you how beautiful everything is, instead of letting you find this out for yourself, and the appeal of every new fruit or creature is swept aside by its being used as the occasion for yet a further sermon on the nature of pleasure.
The central flaw is the problem of any writer in depicting evil: how do you make it obvious enough that it IS evil, but also account for its appeal? It is cheating, and ultimately self-defeating, first to depict the beliefs you dislike, and then to make them more obviously evil by adding a few extra unrelated vices. Weston (the devil figure in this book) is so plausible in his attempts to mislead the new Eve that Ransom does not know how to reply other than by physically removing him from the scene. However, Weston also amuses himself in his spare time by pointlessly mutilating frogs. This is of course explained by a further lecture on the banality of evil and its fundamental hatred of intelligence; but it is a grave tactical mistake, by the author as well as by the devil, as surely all Ransom needed to do was to show a frog to the lady. (In the same way, in That Hideous Strength, the Institute's programme as originally outlined by Devine is already bad enough, without adding gratuitous devil-worship.)
The odd thing is that no one knows these things better than Lewis. For the importance of letting the emotional situation speak for itself, see An Experiment in Criticism; for the blackening of villains by adding an inappropriate vice, see his review of Orwell's 1984. (That, incidentally, is where Brave New World scores heavily: the rulers there are not villains but entirely well-meaning, it is their beliefs that are gently shown to be disastrous.)
OK then, why so many as three stars? The language, as always, is wonderful. Lewis really is, in the words of Beachcomber's spoof review (obviously prophetic of Da Vinci-style tripe), "that rare thing, a writer who can combine breathless excitement with profundity of thought". The Lady's combination of innocence and majesty is perfectly done, and the consideration of the ways in which she does, and does not, need to grow up and of how Ransom's feelings for her are, and are not, sexual is suggestive and moving. The vision at the end is reminiscent of Dante. In showing how each thing in turn, by being utterly different, is in its own way the pivot of creation, it suggests an imaginative solution to the problem of creating a world that is both peaceful and interesting.
Not a book to miss.