Lewin, a distinguished historian of the Soviet period, weighs in to the debate over the meaning of those years in the larger context of Russian history before and after. That is why "U.S.S.R." is sandwiched between two Russias in the title of the book, an amalgam of old and new essays. Those essays that deal with specific subjects--such as the civil war, the background to collectivization, and the early phases of industrialization--are fresh, instructive, and lucidly written. In the book's other parts, where Lewin, in his words, intends to set Russia and the Soviet Union in "historical motion" to interpret the long sweep of history, problems begin to mount. The difficulty is not so much with the building blocks of his theory: the centrality of the struggle to develop the country, its society and economy, the impediments raised by its agrarian base, what the regime has done to society and to itself in the effort, and the alternating, sometimes simultaneous cycles of "rapid change" and "stagnation." Rather the deficiency is in its execution. Too often when the argument needs clarification and development, the author settles for a fragment of the idea or even a wave of the hand and turgid, affected writing.