I have a kind of deluxe edition from them in 2 volumes, one of which is a facsimile of the manuscript and the other is the modern edition, in 88 pages. Assuming that this 2nd volume is the same thing that you're considering, I'd have to say that it's worth it for the historical value only - there's nice background information, a translation (from Latin into German) of the written material in the manuscript, plus the pieces have registrations (which in the manuscript are rather lavishly indicated with pictures of hands pulling the stops). There's a summary of all of this in English, while the complete texts only in German are.
The musical value of the pieces themselves might be charitably described as "slight."
Other variables which I don't know include the price of the thing ....