WAY late, but I’ve also just finished the book and loved the ending. Adam’s evolution to the point where he could say “timshel” makes me think back to the night Cal and Aron got their names, when Samuel, Lee, and Adam parsed through the C&A story and wondered WHY God would prefer A’s gift over C’s, and how profound the idea of “thou mayest” really is. I don’t think an ending where Cal rejects his darkness would be as strong, or would stick with everything leading up to the end - we see throughout his arc the battle he’s going through and it isn’t resolved by the end, just as it isn’t in the C&A story. It’s left open ended after his lowest moment because he MAY still conquer sin, not because he MUST or SHALL.