MALCOLM BRADBURY charts what he sees as the two main impulses of American fiction in the 1960s towards documentary and towards a kind of ' surreal fabulation.' He distinguishes these from the earlier preoccupation of the 1950s - an aesthetic compactness and a concern with human relationships in the chaos of an urban world. The link, he believes, lies in the continuing willingness of the modern American writer ' to risk formal purity in attending to the powers of time.'