HISTORIANS COME IN ALL different shapes and sizes. The well-known ones, those mass-market storytellers we invite into our homes by way of television or bestseller, display enough variety to suit most tastes. There's David McCullough, courtly and urbane as a Renaissance bishop; Ken Burns, bearded and earnest in the required PBS manner; Michael Beschloss, bronzed and well-coiffed as a matinee star; Simon Schama, smooth and subtle. If the past is a foreign country, these are its friendly, unthreatening ambassadors, anecdotal, unflappable, fairly bursting with middlebrow sagacity. They are the bland leading the bland, and none of us is much worse for their agreeable, undemanding guidance. Away from the cameras, less glamorous historians play their part in making the past present--graduate students, assistant professors, archivists, librarians. These are the meek who will not inherit the earth but who labor mighty hard to understand it. Not as famous or as well paid as the big shots, they are actually more important. Without them, our civic life would be a wasteland of forgetfulness, a cultural desert. They tell us who we are by telling us where we came from. They unsettle our pieties, question our assumptions. To be sure, strange ideas sometimes circulate when three or four of them get together. Their politics are often more to the Left than the Right. On the whole, though, these are serious people who demand serious attention. Spare them a thought at Barnes and Noble. They know more than you think.