See, I was fine with the ending and I even understood what Drew was getting at. He posted on his site a little further elaboration that eliminated the ambiguity. And I think it's a nice touch.
*Warning! Don't read unless you want the ending spoiled!
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See, with Bane dead, but with some odd shadow of him left on Zannah, it allows Drew to keep him alive in a respect if he gets to continue writing more books. It adds character to Zannah, and opens up a lot of possibilities for the author. Zannah could have inherited some of his strength, maybe odd memories or traits, things that will always remind Zannah of her master, something to keep her thoughts of him alive as she moves forward with her new apprentice.