Finished the book last night when I only wanted to read a few pages, so let me say somethings here right now:
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For Iron Fist's Stover = Geptun statement, I couldn't agree more. The whole epilogue there immediately made me feel like I had just "watched" the holothriller that Geptun wrote that Luke made him rewrite. The final line about hating rewrites is something I'm sure all authors think when their editors say "nu uh".
For the Dark, I didn't know Stover was going to throw another view of the Force at us! The Dark was a great idea, and you can use it to describe a lot of the events that have happened in the SW universe much like Blackhole did with Palpatine's rise and fall. I'll have to reread the book some time to better understand the Light, but I'm sure it's just an element of the Force that the concept of the Dark deems irrelevant.
However, I think the idea of the Dark would even offend Sith. The Sith philosophy really stresses control over everything by using the Force as a tool. I guess a Sith would embrace this idea to gain power by eliminating their enemies, but will always fall away from the idea when they are in a position of complete control.
Now, best book ever? Sorry, but it still didn't beat Traitor in my eyes, but is still a phenomenal piece of work. And Luke did do some cool things (like using Vastor to cleanse the black metal) but making the trillions of beings in the galaxy believing you are dead except for one, is still the ultimate trick Luke has demonstrated and not making thousands of people die (IMO)
Great book, and I look forward to discussing it on the next episode of EUCast!! 
_________________
"Changes are nice--but so is continuity!"
"Then you saved my life. How disgusting. How unfortunate."
"No, don't gush on so. It was nothing, really."