Crosby, a historian with an ecological perspective, explores the impact of Columbus' voyage on the ecosystems -- and people -- of the New World in this lively and provocative study. He looks not only at the disease and devastation wrought (much of it unintentional) by the Spaniards but also at the exchange and impact on crops, drugs and domesticated animals. 30th anniversary edition.  (GEN21, $33.95)