Essentially, it's ancient Swedish folk music played on violins, bag-pipes, violas, lutes, bowed harps, Jew's harps, bouzouki, electric guitars, and a hurdy-gurdy. Only, instead of folk music, it sounds more like the way Page and Plant were approaching their old Zeppelin tunes during their reunion tour. In fact, it's the sort of raw, windswept tundra, viking-metal that Zeppelin aspired to but never reached during their Hobbit-rock phase.
Klevabergselden is particularly apocolyptic. It's world music, but not the kind that gets played in free trade coffee shops. Think instead of something gothy, like Dead Can Dance or Miranda Sex Garden. This is probably Garmarna's most primal album. They got a lot more polished and industrial on later releases, but most of the fans seem to consider this to be their pinnacle.
Garmarna official site
Garmarna on myspace