There was recently this question about the scene involving the children of the planet Camazotz* and their simultaneous ball bouncing in A Wrinkle in Time. It makes quite an iconic scene, apparently. There were multiple rapid answers, and probably more people (such as myself) who recognized the scene but were too late to answer. Moreovoer, the same scene apparently features in the teaser for the upcoming 2018 movie adaptation.
I had not previously thought about the question, but seeing the scene referenced now, I immediately wondered whether the shadowed planet Camazotz, ruled by IT, the oversize brain incapable of love, was intended specifically as an allegory for communism. In the earthly milieu in which the book was written and takes place (1959 America), the Cold War was a major cultural factor. So I wonder if Madeleine L'Engle ever clarified this question.
(The later books, which represent a somewhat different cosmology and are probably not as good, are more obviously not anti-communist allegories, although they might be allegories for something else.)
*The name "Camazotz" originated as a evil meso-American bat god or race of bat demons. In the Mayan Popol Vuh creation myth, one of these death bats bites the head off one of the primordial hero twins, Hunahpu, when he peeks out of his blowgun. During the interval in which Hunahpu is dead, his head is used as a ball on the ball courts of the underworld gods. It is doubtful, though not impossible, that L'Engle may have intended an allusion to this rather gruesome ball story as well.