Johnathan Chait nails it
Now here is the extremely strange thing about The Forgotten Man: it does not really argue that the New Deal failed. In fact, Shlaes does not make any actual argument at all, though she does venture some bold claims, which she both fails to substantiate and contradicts elsewhere. Reviewing her book in The New York Times, David Leonhardt noted that Shlaes makes her arguments ‘mostly by implication.’ This is putting it kindly. Shlaes introduces the book by asserting her thesis, but she barely even tries to demonstrate it. Instead she chooses to fill nearly four hundred pages with stories that mostly go nowhere. The experience of reading The Forgotten Man is more like talking to an old person who lived through the Depression than it is like reading an actual history of the Depression. Major events get cursory treatment while minor characters, such as an idiosyncratic black preacher or the founder of Alcoholics Anonymous, receive lengthy portraits. Having been prepared for a revisionist argument against the New Deal, I kept wondering if I had picked up the wrong book.