The commentaries between the historical fragments are itself historical. They show the opinion of the time more than anything else, and in that sense this is a historical document in itself. I said earlier that nowadays it would not be needed to buy this, since you can find most of these online nowadays. What you probably cannot find though, are those dated commentaries.
Half of this box I already heard, and I have these already in my collection. This is the complete box for the century, the others are parts of this.