To Your Scattered Bodies Go by Philip José Farmer
British adventurer Richard Francis Burton dies on Earth. He then wakes up in an alien place. He is floating in mid air in a vast dark room filled with uncountable numbers of human bodies, some of which are only half formed. Before Burton can do anything he is confronted by men in a flying vehicle who blast him with a weapon. He next awakes upon the shores of a mysterious river. He is naked and hairless. All around him are other people in a similar situation. No one knows where they are or why they have been brought here although it is soon established that the people there had all died. Shortly after they awaken there is a thunderous roar and a nearby structure, similar to a gigantic stone table, emits a massive blast of electricity. They discover that this structure, nicknamed a grailstone, causes food and other supplies to appear in the grails, metal buckets which everyone found with them upon resurrection. Burton quickly attracts a group of companions to him: the neanderthal Kaz, the science fiction author Peter Jairus Frigate and Alice Liddell the inspiration for Alice in Wonderland. The strangest of these is the extraterrestrial Monat Graatut. Monat explains that he had been part of a small group of beings from Tau Ceti who had arrived on Earth in the early 21st century. When one of their number was accidentally killed by humans, their spaceship automatically responded with a death ray which killed all the people on Earth. Frigate and a few others who were alive at the time confirm Monat's story. Retreating into the nearby woods for safety, Burton's party attempt to relax by chewing some gum provided by their grails. They discover, however, that this gum is a powerful hallucinogen. Under its influence Burton and Alice make love, something which Alice, at least, later regrets.