In this volume—which comes nearer to a full-dress novel anything he has yet given us—C. S. Lewis relates the final adventure of Dr. Ransom, now returned from his planetary travels and living on the outskirts of an English University town. This restriction of the scene to Earth does not mean that the story is less mythical (the author calls it 'a fairy-tale') than Out of the Silent Planet and Perelandra. It means that the Senior Common Room at Bracton College, the quarrel between Jane Studdock and her husband, the National Institute for Co-ordinated Experiments, the tame bear, and the deeply wronged fields and villages of England are here given that more than earthly background, that dimensions of depth which such things (in the author's vies) always have in real life, though not in realistic fiction.  The central danger—the 'hideous strength'—will be enjoyed by all who like a good shocker: it will also have more serious repercussions for those who may have read the author's Abolition of Man.

From the dust jacket

Written during the dark hours immediately before and during the Second World War, C. S. Lewis's Space Trilogy, of which That Hideous Strength is the third volume, stands alongside such works as Albert Camus's The Plague and George Orwell's 1984 as a timely parable that has become timeless, beloved by succeeding generations as much for the sheer wonder of its storytelling as for the significance of its moral concerns.

For the trilogy's central figure, C. S. Lewis created perhaps the most memorable character of his career, the brilliant, clear-eyed, and fiercely brave philologist Dr. Elwin Ransom. Appropriately, Lewis modeled Dr. Ransom on his dear friend J. R. R. Tolkien, for in the scope of its imaginative achievement and the totality of its vision of not one but two imaginary worlds, the Space Trilogy is rivaled in this century only by Tolkien's trilogy The Lord of the Rings. Readers who fall in love with Lewis's fantasy series The Chronicles of Narnia as children unfailingly cherish his Space Trilogy as adults; it, too, brings to life strange and magical realms in which epic battles are fought between the forces of light and those of darkness. But in the many layers of its allegory, and the sophistication and piercing brilliance of its insights into the human condition, it occupies a place among the English language's most extraordinary works for any age, and for all time.

In That Hideous Strength, the final installment of the Space Trilogy, the dark forces that have been repulsed in Out of the Silent Planet and Perelandra are massed for an assault on the planet Earth itself. Word is on the wind that the mighty wizard Merlin has come back to the land of the living after many centuries, holding the key to ultimate power for the force that can find him and bend him to its will. A sinister technocratic organization that is gaining force throughout England, N.I.C.E. (the National Institute of Coordinated Experiments), secretly controlled by humanity's mortal enemies, plans to use Merlin in their plot to "recondition" society. Dr. Ransom forms a countervailing group, Logres, in opposition, and the two groups struggle to a climactic resolution that brings the Space Trilogy to a magnificent, crashing close.

From the Amazon description of the 1996 Scribner edition