I think there were hints of that already in S2, but I don't recall it was mentioned explicitly so far. You could piece that out from the show if you knew what to look for. The books have been more explicit about it earlier in the storyline.
Definitely. I started reading only after watching entire S1. The books are better than the show.
(BTW. I found myself to prefer reading source books after watching a movie/series. In this order, my imagination is already primed by the show, so I don't experience the clash between how I imagined the characters vs. how the producers imagined them.)
