It's not as much being well read as being a side-effect of being Swedish. The Nobel prizes, especially the one in literature, gets huge media coverage here, and the rewarded author's works tend to be (re)published and heavily marketed. (Incidentally, the Swedish booksellers are not happy with the prize going to a playwright this year - drama doesn't sell.)

There is also no reason whatsoever for anyone non-Scandinavian to ever have heard about the likes of Heidenstam or Karlfeldt, but they were the kind of poets whose works my grandparents and my parents generations learned by heart in school, and subsequently tend to quote random lines from in everyday speech.