That Hideous Strength is, to me, the most challenging of his space trilogy. I liked Perelandra best, but only after reading it a second time when a friend pointed out that it was a reimagining of the garden of Eden (I was too young to pick up on that during the first read). Out of the Silent Planet is interesting since the reference is to Earth and how it remains "silent" to those outside of it who choose to avoid its rampant evil.
Incidentally the trilogy came about when C.S. Lewis and J.R.R. Tolkien agreed to write separate sci-fi series - Lewis would write a space trilogy and Tolkien a time-travel one [0]. Tolkien was to write of a traveler from England who visited Numenor (the land of Aragorn's sires) before it drowned in a fate similar to Atlantis. Lewis completed his, but Tolkien did not although much of the material was published in a volume on the history of Middle Earth by his son, Christopher. (Lewis referred to his friend as "that great but dilatory and unmethodical man".) Tolkien's experiment did result in the development of the idea of the Fall of Numenor which did get incorporated into the Lord of the Rings saga.
This unfinished book was dropped in favor of "Perelandra", which I think was a good choice.
Numenor was briefly mentioned in "That Hideous Strength".
In Brazil the first two books were translated to Portuguese but, as far as I know, "Strength" never was. That was probably also a good choice as the more familiar you are with British culture the easier it is to like that book. Even for me it is my least favorite and given that I had a computer project named "Merlin" when I read it I expected to enjoy it more.
Incidentally the trilogy came about when C.S. Lewis and J.R.R. Tolkien agreed to write separate sci-fi series - Lewis would write a space trilogy and Tolkien a time-travel one [0]. Tolkien was to write of a traveler from England who visited Numenor (the land of Aragorn's sires) before it drowned in a fate similar to Atlantis. Lewis completed his, but Tolkien did not although much of the material was published in a volume on the history of Middle Earth by his son, Christopher. (Lewis referred to his friend as "that great but dilatory and unmethodical man".) Tolkien's experiment did result in the development of the idea of the Fall of Numenor which did get incorporated into the Lord of the Rings saga.
[0] https://en.m.wikipedia.org/wiki/The_Lost_Road_and_Other_Writ...