Escape to Witch Mountain probably became more famous, and more widely read, after it was made into a Walt Disney film in 1975. The motion picture Return from Witch Mountain (1978), once more featuring Tony and Tia, was more a sequel to this film version than to the original book. The written sequel was also based on the motion-picture sequel and not on the original book.
Escape to Witch Mountain is clearly science fiction, but it is also in some ways a work of social realism. The tenement situation and the dismal orphanage are real-world occurrences, even if many of the activities of Tony and Tia are not. The prejudice that the two children encounter is also part of the real world. This mixture of social realism, along with the contemporary setting, makes the book different from what is usually considered young adult science fiction, such as those works written by Andre Norton and Robert Heinlein. Placing the alien or the fantastic in the mundane world is Key’s way of showing the dark side of human nature. It is a theme that he pursued in other works as well, such as The Forgotten Door (1965), a winner of the Lewis Carroll Shelf Award. In other works, such as The Magic Meadow (1975) and Flight to the Lonesome Place (1971), his characters flee the hardships of society by escaping to magical places. This combination of the fantastic and the realistic makes Key’s stories thought-provoking as well as entertaining.