It's still a fun and fabulous book. I first read it when I was a preteen or teenager, and the only thing was the struggle between "good" and "evil". I have read it several times since then, and each time I get a little more from it. I doubt that the author intended it to be an allegorical treatise on good versus evil, but it can be twisted and used and interpreted and applied to so many situations that it is easy to create it.
I realized this time that that the main character is only 13. It seems wrong in many ways, except that when I first read it, I was about that, and she seemed so right.
It's about a girl, Meg, who gets involved in a search for her missing scientist father, with her younger (five-year-old) "strange" brother, Charles-Wallace and a 15-year-old boy, Calvin, that she just met but is equivalently (although totally differently) strange. They get taken up by three wacky superhuman women and travel through galaxies and experience true evil incarnate. All of the characters are well-defined, and when you think that there's a chink, you determine that it's really just humanity written in. I strongly recommend this!