The book basically covers, as the title suggests, the intellectual history of economic thought - what currently would be called economics - up to an including Adam Smith's landmark work The Wealth of Nations.
However, as is fitting with Rothbards libertarian background, the book is written with a special eye on free market thoughts.
Moreover, towards the end of the book, Rothbard's agenda becomes clearer and clearer as Adam Smith gets a very, very disfavorable treatment by Rothbard - and with his characteristically vivid use of words.
Thus, the book is not a dispassionate historical account on the evolution of economic thought, but in addition an value-laden evaluation of different schools and trains of thought.
Was it good?
The book is quite monumental, the first volume alone running for nearly 600 pages. The text is very informative and quite often told by focusing on certain key individuals, their careers, thoughts and influences. In the usual Rothbardian style, the text is very enjoyable to read.
However, the value-laden nature of the text starts to become perhaps a bit too striking towards the end of the book - especially considering that the text is (supposedly) academic by nature. In particular, the treatment of Adam Smith is very harsh, as can be seen in the following quote (pp. 435-436):
The problem is that he originated nothing that was true, and that whatever he originated was wrong; that, even in an age that had fewer citations or footnotes than our own, Adam Smith was a shameless plagiarist, acknowledging little or nothing and stealing large chunks ... And even though a plagiarist, he plagiarized badly, adding new fallacies to the truths he lifted ... Wealth of Nations is a huge, sprawling, inchoate, confused tome, rife with vagueness, ambiguity and deep inner contradictions.
You really get the sense that Rothbard was no fan of Smith. However, it must be admitted that Rothbard can write, which makes any book by Rothbard a pleasant reading experience.
The main take-away for me?
In a text like these, there is a wealth of take-aways to be had, from the nature of money or value to the theory of interest rates.
However, perhaps the big meta-take-away for me is the importance of simple problems. Indeed, it seems to me that economic thought has made greatest progress when a clear, well-thought answer to a simple problem has been advanced. As one example, the diamond-water paradox, or the paradox of value, was one such simple problem which lead to the 'marginalist revolution' in economics. Another such example is the question of why is there such a thing as interest (rate for money).
Who should read the book?
Quite obviously, this book is not for everyone already because of its scale and scope. Instead, I presume that the book appeals most to those interested in intellectual history and that in political economy in particular. Moreover, it certainly would not hurt, if one has a favorable attitude towards free market thinking in addition.
The book freely available at Ludwig von Mises Institute: An Austrian Perspective on the History of Economic Thought, Volume 1