You definitely need to watch from the first season, otherwise you won't understand who's who at all - there's only 8 episodes total, so it's not that long. The popularity makes sense: Henry Cavill is a great actor playing Geralt, awesome graphics, interesting characters, plus there's a huge fanbase from Sapkowski's books. I started watching it myself half a year ago when I had free weekends between clients, and now I'm waiting for new seasons like they're gifts. I'd recommend starting it, especially if your friends are already discussing all the details - at least you'll have something to talk about.