Doug -
If what your buddy's got looks like this and R-2800's pic it's the seven-volume bound set that was issued to individual aircraft commanders during training. I've only seen them for the B-24D model. The seven volumes should be Airplane General Manual, Powerplant Manual, Flight Manual, Hydraulic Manual, Electricity Manual, Radio Manual and Armament Manual (see R-2800's pic). They were issued with a leather case to hold them plus some extra paperwork and were embossed, including the case, with Consolidated's logo and such.
I've seen four of these sets sold on eBay during the past two or three months. I dug back through my records and they went for $1,127, $515, $350 and $910. The set that went for $350 may have not had the case with it but I just did a quick check. A lot of it depends on who was bidding and how badly they wanted the set. If you want a list of auction numbers to look at the pics and such for research shoot me a PM and I'll get them to you.
Hope this helps.
Gary