Was it worth it? How does it compare to other books you have read about the time period (this one probably being much larger)?
I have read sections of it, but not the entire thing (obviously). It is tertiary source material; he states in the bibliographical essay that he was "confined to secondary material" and that the primary material was sourced from there. If Rothbard is to be taken at his word and interpretation, absorbing all of it would be comprable to all of the secondary material he mentions.
As for the content I have read, the amount of information in it is staggering. I have typed a few paragraphs, but they do not do justice to what is there. There are too many topics; it is not all about one particular category, but covers many...
I thought it was interesting, but I don't have too much expertise with this.
Schools are labour camps.
For anyone interested, here's the Mises Wiki entry. (The funcitonality of collapsible tables was broken with an installation update, so those contents kind of annoyingly take up the page, but that will be fixed eventually.)
Tom Woods has a copy of the 4-volume edition in his office, which is visible on the shelf behind him in all his videos. Him and Gutzman would probably be the two best judges on this. You might check around to see if they've written anything about it, and if you're inclined, send them a quick email and see what you get back.