The LULU print on demand service has a 3 day 25% discount offer on its entire catalogue, including loads of Wargame rulebooks, scenario books and expansions.
Just a quick trawl through found all the SoBH game books, GW Spearhead, Panzer Korps, Fist full of Tows, Blitzkrieg & Cold War Commander plus loads of related titles.
Discount applies to current prices (some of which are already reduced!), code is:
NEWJUNE25
Works across all the various national sites. Expires 3rd June.