SARAH, PLAIN AND TALL by Patricia MacLachlan...

SARAH, PLAIN AND TALL by Patricia MacLachlan (Harper & Row: $8.70; 58 pp.; ages 8-10). In 1744 England, a quiet revolution began to stir when a farmer’s son with bookselling in his ancestry moved to London. There in St. Paul’s Churchyard, John Newbery opened a two-windowed book shop, published “A Little Pretty Pocket Book,” then displayed an arresting sign: “Juvenile Library.” This was a landmark because until then, with the exception of nursery rhymes and fables, children’s literature had been hornbooks and the sort, designed merely to instruct or improve behavior. That reading could be a child’s pleasure was indeed innovative.

Newbery published only about 20 books in his lifetime, but he was the first to woo youngsters for the sake of entertainment, stories with tiny engraved pictures, flowered bindings and gilt edges. Despite the care with which these volumes were made, they were inexpensive so that folks of modest incomes could afford them. It is in his spirit with excellence that the American Library Assn. each year--since 1922--awards the John Newbery Medal to an author for the most distinguished contribution to American literature for children.

This year’s winner, “Sarah, Plain and Tall,” is historical fiction, slim enough to read in one sitting. It is told beautifully by Anna whose mother died the day after giving birth to her brother Caleb. Their life on the prairie is simple and a little too quiet, especially since “Papa doesn’t sing anymore.” But when he invites a mail-order bride to share their home, new meaning fills their days. Sarah arrives in the spring, a symbolic as well as literal sign of hope and the happiness to come. The exact setting is vague (1800s, Midwest?) but the yearnings of Caleb and Anna are timeless. Their tender musings about having a new mother make this a special story, which is based on a true event in the author’s family history.