I would argue that it is many books, written by an author with Multiple Personality Disorder. There is Goldberg the revisionist historian, Goldberg the outraged conservative child, and Goldberg the troll.
...The most effective chapter is "Woodrow Wilson and the Birth of Liberal Fascism." Goldberg catches Wilson, Herbert Croly (the founder of The New Republic), Walter Lippmann, and other famous progressives of the World War I era with their hands in the fascist cookie jar. ...Above all, they saw war and military conscription as a positive force for molding citizenship and speeding the pace of progress.
I think that the rise of strong centralized governments that took place between 1850 and 1950 in many countries is an interesting phenomenon. I am enough of a technological determinist to believe that it had something to do with railroads and the telegraph (and later the automobile and the telephone), which made central authority easier to implement and more difficult to evade. It also had something to do with cinema, microphones, and radio, which facilitated mass propaganda.
Given the technological environment, the ideologies that emerged--Nazism, socialism, and progressivism--all had a strong centralizing flavor. Goldberg makes an important contribution in pointing out common elements, notwithstanding the aspects of the book that I found unsatisfying.
For more on the book, there is an online interview of Jonah Goldberg by Will Wilkinson. Apparently, I am not the only one who found the chapter on the Woodrow Wilson era the most compelling.