Sanderson is a great writer and he never writes pointless sections or draws things out, this makes his prologues and flashbacks a lot less onerous than other authors. The bit with Kalak in the far past was short enough that it didn't bother me, especially since it was an actual scene and not relayed like some boring history book or a horrible self indulgent section for the PoV of an irrelevant character that drags on endlessly.
I don't hate prologues on principal, I just hate many of the ways authors go about writing them. The prologue on TWoK was short, to the point and interesting. Pawn of Prophecy from Eddings is an example of a prologue that makes me want to never read the book. Steven Erikson is the LORD AND HIGH EMPEROR of self indulgent chapters from random PoVs that make me want to pull my hair out.
I did find the flashback sections in TWoKs somewhat tedious. I don't know why, but I just can't stand long sections of back story that I know have no bearing on what is happening. Character development is my favorite part of novels, but I don't want to spend an hour in the middle of the story having the author show me something they could just as easily have told me.
Sanderson has stated that each book in The Stormlight Archive will focus on a different character's story and while I'm not looking forward to more flashbacks I do think that will be an interesting paradigm.
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