Perelandra, the place, is some of the best, most vivid, most memorable, and most glorious bit of worldbuilding I've ever encountered. I first read the book when I was way too young to understand the philosophy, so I just read and re-read the parts before Ransom meets Eve. The islands, the fruits, the bubbles, the dragon! So wonderful and, as you say, detailed enough to make the patently impossible real.

It's like a dream you wake up from remembering only how wonderful it was, try to return to, and can't. Except Lewis managed to write it. It's an amazing work.

Out of the Silent Planet is very good but not transcendent, and to be fair, it isn't trying to be. Literally the only parts of That Hideous Strength that I like are the mice and the women trying on their magical dresses.