GDG- OR Supplement

[Tom Ryan]

Just came across a reference to the "SUPPLEMENT TO THE OFFICIAL RECORDS OF
THE UNION AND CONFEDERATE ARMIES" by Hewett, Trudeau and Suderow.  Amazon
shows a listing that includes 12 volumes, but it is unavailable.  A search
on Bookfinder.com turns up no matches.

Does anyway have a set, and how useful is it?  Is this material that was
left out of the orginal OR, or something completely different?  Is it
available anywhere, and what is the cost?

Tom