Hailed by national leaders as politically diverse as former Vice President Al Gore and former House Speaker Newt Gingrich, Generations has been heralded by reviewers as a brilliant, if somewhat unsettling, reassessment of where America is heading.

William Strauss and Neil Howe posit the history of America as a succession of generational biographies, beginning in 1584 and encompassing every-one through the children of today. Their bold theory is that each generation belongs to one of four types, and that these types repeat sequentially in a fixed pattern. The vision of...