How Dark is Too Dark?

I finished the outline of The Amanai Resolution last night.  I cannot say that I am as excited as I was with The Amanai Deception.  Maybe it is because I have so much going on right not to really thing about it, or maybe it is because the story is so much darker than the previous books making me feel depressed.  I will mull it over and try a few other ideas before I start writing it.  I can always change the story as I am writing it.  That has happened before with great results.  It will be a while before I can start the book.  I still have to expand the barn, build the leanto on the back of the garage, close the pool all while working my regular job, taking care of the family, and going to school.  No wonder this round is dark and depressing!  Too much shit going on in real life!