SPOILERS
The episode at first really threw me off. There was not a discernible forward-moving plot trajectory, and I was getting antsy because we're approaching the end. Nora's journey seemed like a side quest. And the story felt utterly conventional.
Then, at 22 minutes, when Mark Linn-Baker begins his pitch — "okay, there are a couple types of radiation" — I was fully on board. I expect my expectations to be upended, and that was certainly happening. I then had absolutely no idea what was going to happen from one minute to the next.
I am very strongly reminded of Lost episode 601 ("LAX"), which mercilessly trolls the audience in such a beautiful way — sly but also heartfelt.
The scene were Nora walks in on Kevin (46:40) is pure magic. One of the best scenes of the whole series. Carrie Coon's performance there is truly next-level. I didn't even realize I was crying until that scene was over because I was so utterly captured.
Australian Kevin is... interesting. When he hit the kangaroo, I felt strong parallels with Kevin and the dogs in season 1 ("they're not our roos anymore") and Laurie and the Guilty Remnant in season 2.
They did go a bit over the top with his characterization, though. We're supposed to hate him enough that we don't feel too bad when he dies. I would have been okay with most of that, but I think it crosses a line when he throws the keys. Really puts a button on it. A strange bit of lazy writing that felt out of place in this show.
Thankfully I loved what came next with the four horsewomen of the apocalypse. To your question, Drenk, this is my guess: Kevin's dad has been in communication with Kevin's apostles, and I'm sure they've shared an electronic version of the book. As Mark Linn-Baker told us, everything important is out there in the cloud.
I'm thinking about this mobile radiation unit that Nora is going to "investigate" in Australia, and I can't help but think of the last few episodes of Lost Season 6. There are actually two possible reference points: the electromagnetic energy in "the heart of the island" or the machine that Widmore uses on Desmond, blasting him with said energy. In both cases, it's an experience that no normal human being can possibly survive, but Desmond does, because of his unique properties. What if this radiation unit leads to a similar scenario? Kevin, after all, has some unique properties of his own.