For a mostly spoiler free incentive: The third season delves into material from one of the prequel books and is split between what happened leading to the creation of the Silos and the exact events leading to them being used and how, and a continuation of the story from S1 and S2, and is its own great parallel story. I really can't wait for season 4 and the conclusion. I've seen the preview and it's going to be a satisfying conclusion I can tell.