Neither the viewpoint nor the method will be foreign to anybody who has ever observed a high-style, well-informed gossip in operation. Mr. Davie is deputy editor of England's The Observer and the book collects the articles he wrote for that paper after visiting Washington, D.C., digging the dirt with capitol hostesses, watching the President at close quarters and visiting the LBJ home territory. The author saws up Johnson by using mild praise on the backstroke and devastatingly quotable commentary on the forward thrust. For instance, after assessing the success of the Johnson marriage and top-rating Lady Bird for wifely devotion and political acumen, he quotes a wit who says, ""I think of them as the Macbeths."" While the President's ideological derivations are competently traced back to their Populist origins and his achievements as a politician fairly noted, it is the initial image Davie summoned up that beclouds the book -- that of LBJ picking his nose and fertilizing his conversation with barnyard vulgarisms. And so it goes through a very short book, sharp as a poison-tipped dagger. Personal rather than political criticism for the highly subjective anti-LBJ.