Shame The Adventures of Hergé didn't cut it - as you say, very promising in appearance.

Part of my dad's small collection of French comic books, acquired when he had a holiday job as dry steward on a cross-channel ferry, was Le Rendez-Vous de Sevenoaks, which I didn't understand very well and which freaked me out considerably after the lighter fare of Asterix.

I recently enjoyed a comic book about the German occupation of the Netherlands - aimed at kids, and highly educational, but well-drawn and involving with it:
http://www.annefrank.org/en/Shop/Books/Comic-Book-A-Family-Secret--/