As a Finn, I found this manga absolute blast to read. The ridiculousness of the whole setting is a laugh inducing riot. It's almost sacrilegious in it's depiction of Simo Häyhä and the winter and continuation war. The story is a loose adaptation (to put it mildly) of a real history. It tells the story of ace sniper Simo Häyhä who fights along Finnish forces in the warfront against the red menace. Joining Simo we see a cavalcade of characters each equally loose and wholly fictitious Manga archetypes.
Most of the appeal comes from seeing how the real history events are adapted to this story, and if you are someone who either takes their history seriously or doesn't know the events of the two wars, then I'm afraid you won't get much out of this story. The story itself is quite average on it's own. Don't expect anything else than a dumb schlock.