In his first book for children, art historian Robertson imparts a wealth of information on 15th-century book illumination via a sweet if somewhat hackneyed story. Papa Jacques is the most admired book illustrator in all of Paris, but he is growing old; his shaking hands and poor vision have delayed his work on an important prayer book. And when his glasses break, daughter Marguerite realizes that she must be the one to complete Papa's work. Robertson's descriptions of the materials used in creating an illuminated manuscriptAanimal skins dried for parchment; goose feathers plucked for pens; madder root, parsley, saffron, vermilion and lapis lazuli mixed to make the vivid paints (shown in a four-page gatefold)Aare sandwiched into transparently didactic prose ("Lapis lazuli stone!... To think these came from over mountains and deserts, across rivers..."). Departing from the sly caricatures she created for Lives of the Artists, Lives of the Writers, etc. Hewitt offers realistic watercolors that give a lively sense of the bustling Paris of nearly 600 years ago. Best of all are the illuminated borders she creates for chapter openers, portraying the illustration style described in the text, and the judicious use of gold ink to set off her compositions and her projections of Marguerite's manuscript. Ages 8-up. (Oct.)