Mulkay argues that "Sociologists and philosophers have converged on a conception of science as an interpretative enterprise, in the course of which the nature of the physical world is socially constructed," a move that "brings science fully within the scope of the sociology of knowledge" (95). Although largely correct, there isn't much original work here, even for 1979, so it's best seen as trying to synthesize what had been produced until then.
Note: He provides a summary of the book at the end, from p. 118 to 122.