Many physicists are continuing to work toward the fabled goal of a “theory of everything.” A successful theory would unify the four known physical forces – gravity, electromagnetism, and the nuclear strong and weak forces – and case some light upon newly discovered cosmological phenomena and puzzles. Quite a few theoreticians are attempting to use postulated extra dimensions to come up with a workable product; fantastic as it may seem, a universe containing ten or 11 dimensions offers considerable promise. Halpern (physics & mathematics, Univ. of the Sciences, Philadelphia) takes a historical approach to examining the advancement of multidimensional theory. Kaluza, Klein, Einstein, and many other contributors over the past 100 years are discussed, and their work is described at a level appropriate for a general audience. Only Halpern’s terminology and the pace of the discussion in the last few chapters will challenge nonspecialists.