Startling alternative history has been a popular sub-genre of military history and science fiction for years and has recently reached new heights of popularity with Harry Turtledove's epic alternative histories of WWII and the American Civil War. Gregory Benford, Hugo and Nebula Award winning author, here collects original stories by such luminaries as Poul Anderson, Larry Niven, Frederik Pohl, Kim Stanley Robinson and Robert Silverberg in alternative histories from ancient times to the 20th century.