While government is shrinking elsewhere, its presence on the World Wide Web seems to be growing. Literary agent and now author Raphael Sagalyn has compiled the first comprehensive guide to the voluminous reliable and tax-supported U.S. government information available through federal agency Web sites. Just published, The Great American Web Book (Times Books, $17) lists the well-known (The Library of Congress) and the less known (The Educational Resources Information Center) with annotated listings organized by government branch.