See also my reviews of Season 1 or Season 2. The short version is this: when Axl Johnson turned 21 (at the beginning of Season 1), his brothers took him out into the woods, gave him a sword, and lightning hit him. At which point he discovered that he was a reincarnated Norse God - with very limited powers. Odin, specifically. And this was a big moment for his brothers, because they're all minor gods and the appearance of Odin could potentially mean that they'll all regain their full powers ... if the reincarnation of Odin is united with the reincarnation of Frigg. So we've already had two seasons of the brothers trying to track her down.
My favourite episodes all involved Thor: he appears in one episode in each season(?), and Geoff Dolan does a wonderful job of their vision of an overweight goat farmer with a temper as Thor.
I had considerably less trouble with the New Zealand version of English than I expected ... and a good deal more trouble with their expressions. I now know that "munted" means not merely drunk, but so drunk (or messed up) as to not be functional. And it can also be applied to any piece of equipment ("this car is munted"). And that "having a root" means to have sex. And that a "fancy dress party" doesn't mean what we think (ie. suit and tie), but rather what we'd think of as a "costume party." And that was actually one of my biggest issues with the show: Axl (in fact nearly everyone) gets into a staggering variety of costumes across three seasons: at least one dress a season for Axl, his underwear on multiple occasions, butt naked fairly frequently, and on one memorable occasion, a merkin.
This is the weakest of the three seasons, with the writing reaching farther and farther afield to try to bring in interesting elements of mythology to keep us entertained, and turning their human lives into a soap opera. One of the things I particularly liked about the first season was the family bond between the brothers. Toward the end of this season they completely tear that apart, especially in the last three episodes. I thought "oh shit, you're just trying to ratchet up the tension before the inevitable cliffhanger ending before the fourth season you never got." And I believed that right up until the last half hour of the last episode when I finally realized they had actually known the end was coming and had written for it, which was a huge relief: I forgave them a lot for that. The ending was actually pretty good. Despite which ... if you want my recommendation, watch the first season and stop there.