As always, L'Engle achieves the task of explaining scientific and cosmic theories to her audience of children & adolescents without talking down to them. And this time without a character quoting the Bible every chapter. While I'm fairly certain that her ideas about symbiotic mitochondria are off (I haven't taken a biology course in ten years), she is correct about your body being a galaxy for its cells. I also loved her idea of kything, and am totally using it as a euphemism for sex. Despite all that I liked about A Wind in the Door, I'm sorry to say that the new supporting characters, aside from Proginoskes, just didn't measure up to the three Mrs. and Aunt Beast. But then again, they probably weren't meant to.