The genre has come a long way over four centuries. "Early children's books tended to be solemn and purposeful," Marcus says. "They were created to teach a moral lesson of some kind and they spoke to the child from on high. This approach worked well enough for groups with a fundamentalist view of life—the Puritans for instance—and with certain basic lessons that needed to be communicated as early as possible. But other kinds of books for children began to appear by the mid-1700s. Under the influence of John Locke and his observations about how children learn and grow, this new kind of children's book showed a greater awareness of children's interests and capabilities."

Once considered chattle, children had to be fed and trained. But as they came to be seen as young people, books aimed at them evolved from strictly didactic to fantastical. "Curiosity was seen as a virtue not a vice," Marcus says. "Humor was recognized as a key to engaging the child's interest. The child's attention span was taken increasingly into account. Illustrations were emphasized and made more interesting. By the middle of the 1800s, a few writers and artists like Edward Lear and Lewis Carroll recognized that playfulness could be an end in itself in a children's book and that children could be trusted enough to make irreverence toward the adult world a major source of merriment in their books."

An explosion of creativity occurred during the late 19th and early 20th centuries. New classics were forged, ranging from simple picture books like Goodnight Moon and The Very Hungry Caterpillar to beginning readers like Little Bear and The Cat in the Hat to realistic teen fiction to, most recently, graphic novels for preteens, teens, and younger readers. "The downside of all this," Marcus says, "has been the commercialization and globalization of publishing, which has led to a certain preference for the slick and the generic; to picture books that look like ads for themselves; to fantasy novels that read like treatments for the Hollywood films they are hoping to become."

"The ABC of It" is not a greatest-hits or march-through-history survey. Marcus has set a stage for viewers to step back and see the books in the larger context of the arts, popular culture, and social history. "Puritans believed that children were born sinful," he says, by way of example. "Children had to learn to read the Bible as soon as possible! But the Enlightenment philosopher John Locke believed children were not sinful at all, and that what they really needed and wanted was playful books with pictures. His ideas, which date all the way back to the 1690s, read like a blueprint for much of what we think of today as a good children's book."

So to the list of reasons why children's books matter, add the way that they reflect the times they were created in. "They are the message-in-a-bottle that each generation tosses out to the next generation," Marcus says, "the record of one generation's hopes and dreams for the next."

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