the GURPS WWII books are more overviews of the war era than specific missions or adventure hooks.
they give lots of really great (and useful) information on the time period, the combatants, and the progress of the war.
so far, there's been a main
GURPS WWII sourcebook;
Iron Cross, the Germany sourcebook;
Return to Honor, the France sourcebook; and
Hand of Steel, the commando sourcebook. the latter two are short -- maybe 30-40 pages? -- but densely packed with material. an American G.I. sourcebook is slated for February.
if you don't mind doing conversions, there's lots of stuff to steal from the line. GURPS templates are readymade characters, that can give an idea about what kinds of skills and abilities different types of characters should have (rifleman, fighter pilot, resistance fighter, Gestapo agent, etc.). there are lots of weapons and vehicle stats provided as well. (and the vehicles use a much-simplified version of the GURPS Vehicles design system.)
basically, it's like taking a shelf of WWII history books and pulling out just the pieces a gamer would be interested in.
as far as adventure material goes, GURPS has never been big on selling adventures. however,
Hand of Steel (the commando book) does have a chapter on typical commando missions that might come in handy in trying to figure out what the PCs could be doing during the war. also, if you plan on doing anything in occupied France,
Return to Honor has good information on the French Resistance (which was a lot more complex than i had ever imagined...).
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