Amity Shlaes has written a powerful book. It is the most interesting and substantive account of Lyndon Johnson and Richard Nixon’s “war on poverty” to date — and just in time. In Great Society: A New History, she notes that “just as the 1960s forgot the failures of the 1930s, we today forget the failures of the 1960s.” Shlaes has written 510 pages of argumentation, with detailed description and telling digression that traces the arc from the unbridled hopes of the early Sixties to the enormous administrative expansion of the “second New Deal” to the missteps in implementing it that became all too apparent in …