This creative young adult novel has seen some film adaptations in recent years, but none have been terribly well received. That's something of a pity, because the book is quite sophisticated, but I think much of the allegory and depth is lost when it ends up a dumbed-down Disney movie.
The author also has an interesting story, having been raised in Manhattan, and then on to boarding school in Switzerland. She earned an English degree from Smith College. This was one of her mid-career novels, written between 1959-1960, so it was definitely influenced by an age in transition. Apparently, it was rejected some twenty-six times, before it was finally accepted. Despite a somewhat rocky start, the novel became wildly successful, and spawned an entire series which eventually included five books. The first won the coveted Newberry Medal in 1963, an estimable accolade for a children's book, but it doesn't strike me particularity as children's literature, and perhaps that's the point.
The main protagonist is an awkward girl at an awkward age: thirteen-year-old Meg Murry has a tough time with just about everything. She's bright, but is viewed as a lackluster student (I wonder how much this mirrors the author's own experiences) who is labeled a troublemaker. She gets into fights with people who insult her family, particularly when anyone talks about her youngest brother, often considered to be an idiot (he's actually a misunderstood, stunning child prodigy whose intellectual capacities are so advanced that he's capable of telepathy). Enter another oddball, fifteen-year-old Calvin, who kind of just crosses Meg's path, or so it would seem. Together, the team is swept up in adventure, in the form of three ... beings... Whatsit, Who and Which, who transport the trio to far dimensions, in search of her lost father, a government scientist who has been missing from the family for a year. Despite her scientist mother's desperate searching, it seems that her father has vanished.
The enemy of goodness and light is simply called "The Black Thing," a disembodied supernatural figure who likewise is telepathic, and can possess its victims. I won't include too many spoilers, save to say that the novel is a capable adventure story, which is quite sophisticated for its intended audience. Unless, of course, you're like young Charles Warren.
Many have noted the subtly imbued religious themes throughout the novel, especially the overarching notion that love is the most powerful force in the universe. Some critics' interpretations of it have been somewhat overwrought, however: for example, one prominent scholar has argued that the focus on love and light directly represents Christian love of God and Christ, but I think that's a simplistic over-reading the text, as most religions have love and goodness as a central theme, the one most important to emulate. The author was apparently quite a devout Episcopalian, but I question how much direct reflection the book is of her particular Christian beliefs. As above, I think that it could represent any number of faiths and belief systems, perhaps with the notion that there is no "true" religion, as the principles of love, light and goodness are universal. Seems rather anti-religious-establishment, to me, in fact.
Others have noted that it has a fairly vociferous feminist agenda to it, particularly in the empowered young girl as the main character, which was unusual in a science fiction story at the time. Meg is far from the stereotypical heroine of books in the 50s: she's good at math, and is something of a "tomboy" (but I dislike the term), certainly not the stereotypical demure model girls were expected to emulate. Perhaps what's most intriguing about it is that people seem to read into it what appeals to them, and that's a defining characteristic of a well-told story. Everyone gets something out of it, and interprets its deeper meanings according to their own individual tastes and experiences. To that end, it's certain to be a novel that will remain a popular one for some time to come, appealing to new generations of readers.