World of Ptavvs is part of a long tradition of stories dealing with the first contact between man and alien beings beginning with H. G. Wells's The War of the Worlds (1898) and including Robert Heinlein's The Puppet Masters (1963), Arthur C. Clarke's Childhood's End (1953), and Ray Bradbury's The Martian Chronicles (1950). In such works, the author can make his statements about the unknown. If the aliens are friendly, threatening, or simply enigmatic, so is the universe. World of Ptavvs is closely related to The Puppet Masters in that in both books the aliens are hostile and can control humans. Some critics see both novels as commentaries on the Cold War, with the aliens symbolic of servile communism and the humans the representatives of the libertarian West. Although this interpretation is valid at one level, these novels also deal with the question of what men will encounter as they...