This is a fantasy novel by C.S. Lewis. Like the other two novels in his space trilogy, it has some of the trappings of science fiction, but it is much more unambiguously a fantasy novel at the core. Like the previous two novels, it has a lot of Christian imagery.

This is a classical battle between good and evil, but the protagonists' roles are a little hard to sum up. Is this a contest as to whom can be the first to make contact with Merlin of Camelot woken from his ancient sleep, parallel to a metaphorical battle as to which side is more suited to claim his traditional magic? Is it the story of a woman trying to understand her unsettling prophetic dreams while her husband becomes involved with unimaginable horrors? Is it a few glimpses of a greater battle, for the most part unknowable?

Much of the book is set at a small English university. If you have no trouble suspending your disbelief while corrupt scientists turn towards supernatural evil under another name, you might enjoy this. Much of the nasty politics has a genuine flavor.