Twenty leading science fiction authors, including Stephen Baxter, Brian W. Aldiss, Philip K. Dick, and Connie Willis, chronicle the changes and surprises that might befall humanity in the centuries to come. Is the ultimate Utopia heaven or hell? asks Robert Sheckley in his “A Ticket to Tranai.” In “The Infinite Assassin,” Greg Egan polices the multiverse for murderers of their alternate selves. Geoffrey A. Landis plumbs the depths of a black hole in “Approaching Perimelasma.” These and other stories by James White, Eric Frank Russell, Robert Reed, H. Beam Piper, H. Chandler Elliott, and many others make this one of the most entertaining and thought-provoking science fiction anthologies in light-years.