Crisis on Multiple Earths Book 1: Crossing Over

"From legendary comics writers Gardner Fox and Dennis O’Neil come the incredible crossover events between the Justice League of America and the Justice Society of America that launched the DC Multiverse as we know it! This collection brings together the earliest adventures of the heroes of two Earths as they battle their own arch-foes, the doppelgänger villains of Earth-Three known as the Crime Society, and more!<p>Collects Justice League of America #21-22, #29-30, #37-38, #46-47, #55-56, #64-65, #73-74, #76, and #82-83."