Castañeda, the distinguished political scientist who recently became Mexican President Vicente Fox's foreign minister, describes his insightful book as an "archeology of presidential successions in Mexico." The reader travels inside the "black box" of Mexico's politics during the regime of the Institutional Revolutionary Party, an entrenched political system that the Peruvian novelist Mario Vargas Llosa once dubbed the "perfect dictatorship." Central to this system was the well-choreographed, enigmatic, insiders' ritual for choosing presidents, which persisted from the 1930s until last year. It worked for so long because it was both definitive and generous. No one could question the president's decision on his successor, and losers were well rewarded (or just excluded from power). Last July, however, Mexico achieved a genuine transfer of power through the ballot box for the first time. That opportunity resulted in part from the bitter war between former President Ernesto Zedillo and his predecessor Carlos Salinas, which prompted Zedillo to abandon the old ritual and allow the transition to be decided by an election. That story is unfortunately not told here, but Castañeda is well placed to add it to a future edition of this indispensable contribution to Mexican history.