In his customary Crusty Wise Uncle manner, Mr. Johnson looks over the formation and disintegration of the British Empire and extracts a lesson for US: ""An empire endures just so long as it is worth what it costs."" Organized around salient personalities--the Pitt family, Napoleon, Clive, Hastings (his successor in India) and Raffles (their counterpart in the Far East), George Canning, Palmerston, Disraeli and Gladstone, Joseph Chamberlain, Rhodes, Gandhi--is a running illustration of the theme which is colorful if irregular history. Exception can be taken to some of the assertions (e.g. Clive's lack of cupidity) and more of the omissions--Chamberlain's support of Rhodes is referred to, for example, but there's no mention of his position (colonial secretary) or his program (an imperial federation). Often, indeed, the text seems to dwell on an individual's traits at the expense of his activities. But Mr. Johnson is never dull; neither, sketchy as this is, should he be faulted on that score. What the book lacks in thoroughness (limiting its use for reference) it compensates for by the sweep of its synthesis, the snap of its insights.