This is the third book in a classic trilogy of children's books that begins with A Wrinkle in Time. It's shelved in the section for the seven to thirteen set, but I've only now read it for the first time as an adult. There are some children's or young adult books I've first read as an adult I've loved without qualification, but this isn't one of them. I wouldn't put this up there with such books by Lewis Carroll, Philip Pullman, C.S. Lewis or J.K. Rowling. I don't think the writing, world-building or characters are as strong. However, I'd probably have loved L'Engle's books had I first read them as a child. And for what it's worth, I liked the second book, A Wind Through the Door more than the first book, and this third book most of all. Meg, Charles and Calvin, the children at the center of these books, did grow on me--and grew up--in this trilogy. I knew going in from a friend who loves these that, like Narnia, (or even Potter for all that it's subtle) that these are Christian fiction. It's not as blatant as in Narnia; while I thought Lewis knocked you over the head with the religious aspects, with L'Engle--despite some Biblical quotes and angel characters--in the first two books of Time it was more a gentle tap. This one feels more overtly religious in plot and theme than the others, although it still didn't strike me as overly polemical. This book is different in other respects too. In contrast to C.S. Lewis, who can come across as anti-science, anti-reason, anti-tech L'Engle obviously loves science, which is deeply entwined in the plots of the first two books, which are more science fiction than fantasy. The "wrinkle in time" of the first book refers to Relativistic physics, and the second book hinges on a journey inside a mitochondria. L'Engle doesn't play with science quite in the sophisticated ways Pullman did in His Dark Materials, but I did appreciate that aspect. However, although there are references to science here and there in A Swiftly Tilting Planet, this really is fantasy rather than science fiction, with a flying unicorn taking Charles through a journey in time. Indeed, given the historical fiction aspects, I'd call this a historical fantasy more than anything. We spend time in pre-Columbian America, Puritan New England in the time of the witch trials, post-Civil War America and on to the present day of the book. It was quite a ride, and one that I largely enjoyed.