The all-too-brief period of relative tranquility that extended from the end of the Cold War to the beginning of the War on Terror is the subject of William L. O'Neill's brilliant new study of recent American history. Mr. O'Neill's sharp eye for the telling incident and the apt quotation combine with an acute historical judgment to make A Bubble in Time a compellingly readable informal history. The first Gulf War and President Clinton's interventions abroad notwithstanding, American spirits were freer from fear than they had been since the 1920s, the author argues. No world war loomed before...