He became a nationally known illustrator before he became an author. After he began writing novels for young people, he moved his family to the North Carolina mountains, and most of his books include that wild and rugged landscape.
His novel Escape to Witch Mountain was made into a popular live-action film by Disney in 1975, 1995, and again in 2009. The sequel was made into another popular film in 1978. His novel The Incredible Tide became a popular anime series called Future Boy Conan in 1978.
He is known for his portrayals of alien but human-looking people who have tremendously strong psychic/psionic abilities and a close communion with nature, and who can telepathically speak with animals. In his nonfiction book The Strange White Doves, he professed his belief that animals are conscious, thinking, feeling, perceiving, independent, and self-aware intelligent beings, and have subtle ways of communicating, perhaps via empathy or telepathy. The protagonists of Key's books are often ostracized, feared, or persecuted because of their astonishing abilities or extraterrestrial origins, and Key uses this as a clear metaphor for racism and other prejudice.
In several of his novels (most notably The Case of the Vanishing Boy), Key portrays some sort of communal withdrawal from society by a group of like-minded individuals. Key sometimes depicted government-sponsored social services for children as inefficient or even counterproductive in its efforts: in The Forgotten Door, social services is presented as a clearly undesirable alternative for the protagonist Little Jon, and in Escape to Witch Mountain, Tony and Tia actively flee the system. In both cases, however, it is for a very logical reason: the characters are "not from around here." All they want to do is go home and, happily, a few of us locals have the decency to help them do so (Key's The Forgotten Door predates E.T. the Extra-Terrestrial by over 10 years).
The plot of Key's The Magic Meadow is even more poignant for any reader who has ever been bedridden in a hospital. Its ending in particular is phenomenally optimistic. That was another Alexander Key theme: that good and decent people deserve to escape to a place worthy of them.
As illustrator only
- In the Light of Myth: Selections from the World's Myths, compiled and interpreted by Rannie B. Baker (1925) OCLC 593232
- Real Legends of New England, G. Waldo Browne (1930) OCLC 1710918
- The Book of Dragons, selected and edited by O. Muiriel Fuller (1931) OCLC 2391529
- Suwannee River: Strange Green Land, Cecile Hulse Matschat (1938) OCLC 484454
- The Red Eagle: A Tale for Young Aviators (1930) OCLC 3442600
- Liberty or Death (1936)
- With Daniel Boone on the Caroliny Trail (1941)
- The Wrath and the Wind (1949)
- Island light (1950)
- Sprockets: A Little Robot (1963)
- Rivets and Sprockets (1964)
- The Forgotten Door (1965) OCLC 0590403982
- Bolts: a Robot Dog (1966)
- Mystery of the Sassafras Chair (1968)
- Escape to Witch Mountain (1968) OCLC 436504
- The Golden Enemy (1969)
- The Incredible Tide (1970)
- Flight to the Lonesome Place (1971)
- The Strange White Doves (1972)
- The Preposterous Adventures of Swimmer (1973)
- The Magic Meadow (1975)
- Jagger, the Dog from Elsewhere (1976)
- The Sword of Aradel (1977)
- Return from Witch Mountain (1978) – by Key based on the Disney motion picture; screenplay by Malcolm Marmorstein, based on characters created by Key OCLC 3542494
- The Case of the Vanishing Boy (1979)
- "The Earth Library". Archived from the original on 2005-02-18. Retrieved 2005-04-03.CS1 maint: bot: original URL status unknown (link) Read some of Mr. Key's out-of-print books online.
- "Gone But Not Forgotten: Alexander Key"—The Bulletin of the Center for Children's Books, University of Illinois, November 2002
- The Forgotten Door, a three-episode television series based on Key's novel of the same name, distributed by ITV and broadcast in 1966
- Alexander Key: A Forgotten Author?
- Alexander Key at the Internet Speculative Fiction Database
- Alexander Key at Find a Grave
- Alexander Key at Library of Congress Authorities, with 35 catalog records