Some K words I'm noodling with: Keeper Knowledge Key Kernel Knife
and W words: Weep Will Wisdom Wax Widow Worth Wrath Weapon Wedgie Weather Weapon
The book titles tend to be more metaphorical and flowery than literal (if you read WOK or WOR without knowing what the tiles were, I don't think you'd pick those titles out for those books). I also think he'll avoid repeating any words already used, so no kings, way, words, war. I think Kill is too active a word for the kind of in-world books they tend to feature. Keeper of Winds, or Kernel of Wrath are possibles. I find Keeper of Wisdom too cliched. Though it's a bit meaningless, Knife of Will has the right kind of balance to it, I think. Or for the jokey ones Knowledge of Wedgies for the worst of all possible Braizian punishments and Kaladin on Wayne for the worldhopper slashfic you never knew you wanted.