The central argument of this book is that our ideas about economics and economic policy have long-standing roots in religious thinking. ... The influence of religious thinking bears on how Americans today, along with citizens of other Western countries, think about many of the most highly contested economic policies of our time.
This statement of purpose from the introduction misrepresents the book. The book spends far more time providing a detailed history of (American) Protestant thought on the subject of human agency and destiny than it does on economic theory. It addressed the supposed influence on Americans today only in the last chapter, 29 pages out of 415. Most critically, though, Friedman fails to make the case that religious thinking exerted a decisive influence on economic thinking.
To be sure, most educated people in Adam Smith's time (the mid-eighteenth century) were clergymen, and there was no separation or antagonism between religion and science, seen as a way to "learn about aspects of the divine by studying the world God had created." Debates about predestination and the depravity of man were raging at the same time as Smith's explanation of markets, but rather than direct influence I see two areas of thought reacting to the Enlightenment's law-governed, human-centered Weltanschauung.
Friedman frequently notes how both religious and economic thought in America were influenced by its unique circumstances (a surfeit of land, no pre-established institutions, expanded economic opportunities, confident optimism). Again, I interpret the history as parallel responses to prior conditions. Friedman sometimes seems to agree:
The changes in the conduct of religious life in America were therefore of a piece with the democratic consequences of the Revolution... In one area of the nation's life after another... the authority of established elites eroded while new groups lacking professional training and credentials gained sway.
Luckily, I was interested in the religious history for its own sake. It was interesting to note the correlation between social pessimism and religious fatalism. One doctrine I was pleased to learn about was how our differing circumstances are a blessing from God:
For what other reason, do you suppose, has he given to different countries such different soils and climates and productions, but that they should freely exchange with each other, and thus all be happier and more comfortable? (John McVickar 1837)
It is evidently the will of our Creator, that but few of these objects, every one of which is necessary to the happiness of every individual, should be produced except in particular districts (Francis Wayland 1837)
In passing, I also just noticed the relationship between the words "vice" and "vicious."