Madeleine L'Engle was a faith and reason Christian who was first of all a storyteller. MyGuy says her science only holds up enough to hang the story on - i'm not the one to ask about that. And my theology is not the same as hers, but what stories. They are unquestionably faith stories, and faith-strenghtening stories..
Conservative Christians - and i do count myself loosely in the number - are often offended by L'Engle's books. There are details in them that must be taken as part of a fantastic story. Although a Newbery Award winner, A Wrinkle in Time "is on the American Library Association list of the 100 Most Frequently Challenged Books of 1990–2000 at number 22."
Throughout these three books, i was impressed by the continuity of the themes of the importance of active love, the control of our Creator over all, and joy in finding our God-ordained place in this world. The Murry family is not a churchy family, but the supernatural beings interacting with them know and reverence to God. They quote Scripture in His praise and to encourage the young protagonists to do the hard tasks that need doing. L'Engle looks at good and evil, conformity and being willing to be different, arrogance and humility, the vast spread of our smallest choices.
A lot of the story is truly fantastic. But God moves in fantastic ways, and these are after all stories, and scifi/fantasy stories at that. Why shouldn't they be fantastic? Fiction is about a suspension of disbelief in the details so that we can see a greater truth.
Finally, i would like to share a quote from Madeleine L'Engle herself which sums up the ideas in these books:
. . . what we must look for is not the destructive power but the vision of interrelatedness that is desperately needed on this fragmented planet. We are indeed part of a universe. We belong to each other; the fall of every sparrow is noted, every tear we shed is collected in the Creator's bottle. ”