By the time this Article appears, nearly a decade will have passed since the U.S. Supreme Court declared the Federal Sentencing Guidelines constitutionally dead, and in its next breath resurrected them in advisory form. From the point of view of the federal bench and bar, and of the academics who earn their daily crust watching lawyers at play, the years since the Booker decision have been a turbulent time. The Supreme Court itself has issued more than twenty decisions construing, clarifying, or applying one aspect or another of Booker doctrine. Federal appellate courts have cited Booker more than 10,000 times and federal district courts have published more than 8,000 opinions mentioning Booker. Academics have written over 2,200 journal articles citing Booker and more than 220 with Booker in the title. From a lawyer’s perspective, it is hardly surprising that Booker should have generated so much high-voltage controversy. To undertake a conversation about Booker is to plunge into an intellectual bouillabaisse in which constitutional theory, criminal sentencing theory, inter-branch rivalries between the executive, judicial, and legislative arms of the federal government, tricky points of statutory interpretation, and pragmatic considerations of crime control, criminal justice administration, and the fate of individual criminal defendants are all bubbling merrily about. Moreover, the transformation of the Federal Sentencing Guidelines from a binding to a purely advisory system has not merely been the source of countless procedural wrangles and the fodder for a long cerebral feast, but it has unquestionably altered thousands of individual sentencing outcomes. And yet, from the points of view of federal defendants in the mass and of the system that processes them from arrest to prison gate, perhaps the most surprising fact about Booker is just how small an effect it has actually had. This Article examines the tenacity of the Sentencing Guidelines regime and considers its implications for those who practice in the federal courts and those who aspire to change federal sentencing outcomes.