"Perelandra" is one of C. S. Lewis' finest works, in my opinion. It is the second book in Lewis' Sci-Fi trilogy, the first being "Out of the Silent Planet" and the last is "That Hideous Strength."
"Perelandra" follows Elwin Ransom as he ventures to Perelandra, Venus to us humans. If you're unfamiliar with these stories, Ransom was kidnapped in "Out of the Silent Planet" and taken to Malacandra, or Mars, by Professor Weston and Mr. Devin. In the second book, Ransom is taken to Venus on a mission by the Oyarsa, an angelic ruler first encountered in "OOTSP."
On Venus a new Garden of Eden has been established, and Professor Weston, being possessed, is sent to corrupt this new Eden. Ransom encounters a whole new world, literally, since he comes across colors, creatures, and plants he has never seen before. He meets the Eve of Perelandra, Tinidril, who is searching for her Adam. Tinidril is stark naked but is unaware of her nudity. The story evaluates the possibility of life without The Fall of Man.
Weston arrives in his spaceship, claiming to be a changed man believing in a higher power, and soon meets Tinidril and soon starts to tempt to her. Ransom realizes that he must not let this happen. Obviously, Ransom has been sent to prevent the corruption which Weston was sent to do. The story climaxes as Ransom begins to prevent this temptation.
I don't want to give away too much since the excitement comes from reading what actually happens. It is an exciting book, and leads to interesting imaginative possibilities since most of what is described has never been seen. It could be anything in your head.