THE AMERICAN BILLBOARD: 100 Years by James Fraser (Abrams: $49.50; 192 pp.). Almost by definition, a billboard is too big for a book, even one that can open, as this one does, to a handsome 28 inches wide. Still, this volume, written with access to the archives of the Outdoor Advertising Assn. of America, does a fine job of not only showing us some of the most traffic-stopping of these highway behemoths but filling us in on tidbits of billboard history as well. It all gives a pleasant cultural sheen to the rough and ready art form that poster designer A. M. Cassandre neatly characterized as "putting on one-act plays to a five-second audience."