by C.S. Lewis
written for ages 15-18 | highly recommended
published in 2005 (1943) | HarperCollins

Elwin Ransome, a Cambridge don on a walking holiday, is looking for shelter for the night and chances upon two men, one of whom he knew at school, who drug him and take him with them to Mars in their spaceship. On arrival, he escapes and lives several months with the Hross, one of the three intelligent species (Hnau) indigenous to Mars, learning their language in the process. He meets the eldilic Oyarsa of Mars, an angelic being who is the guardian of the planet. This being sends the three humans back to Earth (known the the other inhabitants of the solar system as the Silent Planet because of a barricade imposed after the fall of its Oyarsa).

Although the premise of the story is a trip in a spaceship to Mars, this book is not science fiction in the generally accepted sense. All is described through the eyes of Ransome who has little or no technical knowledge, and therefore technological details are lightly skipped over. The fiction weaved here by Lewis and which he elaborates in the later books in the trilogy concern the existence of non-human intelligent beings on another planet, and of interplanetary spiritual beings (related unclearly to angels) who are as much servants as we of Maledil (God). A fascinating reconciliation of science fiction and theology.