Scholarly books often resemble the pyramids erected for minor officials in ancient Egypt. Impressive in their way -- and built to last -- they are, nonetheless, difficult to tell apart. By contrast, The Sources of Social Power, by Michael Mann, a professor of sociology at the University of California at Los Angeles and a visiting research professor at Queens University Belfast, is "audacious in scope, ambitious in objective, and provocative in challenge," as the American Sociological Association put it in presenting Mr. Mann its 1988 award for distinguished scholarly publication.