Steig, W. (1969). Sylvester and the Magic Pebble. New York: Simon & Schuster.
Despite the Caldecott Award, this book is also among the banned books list, so cited because the book's material was considered too dark for children.
The book certainly has unusually serious overtones for a children's book. In brightly colored watercolor, the story follows Sylvester, a young donkey who discovers a pebble that grants wishes. Before he can utilize its potential, though, he is attacked, and in panic he wishes himself into a rock, where he's trapped until his parents discover him.
The surprising thing of this book, and what rendered it controversial, is that the consequences of Sylvester's disappearance is shown in stark relief. His parents grow more and more panicked, shown searching, asking the neighbors, and finally mourning for their presumably dead child.
In children's books, it's rarely shown how disappearances affect their families; the point of view stays with the child. And it's true that the parents' grief is moving and sad, but I find it a strength of the book, a more realistic approach.
I've mostly focused on the responses of the parents here, and the ingenuity of Sylvester. Other reviewers have focused on different parts.
Common Sense Media says that it "addresses one of childhood's biggest latent fears, abandonment," and thereby interprets Sylvester's stony imprisonment as an acting out of a child's fear of parental leaving. I saw it completely differently, as an ingenuous solution to Sylvester's being attacked, which then became a problem that Sylvester's parents manage to unwittingly save him from. However, Common Sense Media also agrees with me on the quality: "So much feeling and nuance stuffed into the simple story and pictures of this little book will make children appreciate the power of books and convince their parents that books should be collected and read over and over."
The Judd Brothers took a different interpretation as well, taking the message that "the real beauty of the tale lies in the timeless message that it is not "things" that will make us happy, but the comforts of family and home." I'm more willing to accept this, though I hadn't thought that much about it, because the magic pebble is locked away, to prevent it from doing any damage to anyone. The brothers also declare it a classic; this story is pretty universally beloved, looks like.
The illustrations are bright and clear, the story is moving and a strong combo of fanciful and pragmatic. It belongs in children's libraries.