The story refers heavily to Avant l'Incal, and it's a shame that that book is out of print. This time the light power represents organic life, and the dark power represents artifical life. It seems that John must bring the Incal back together to create an antidote to a virus that is destroying all organic life. To say any more would be giving too much away. Both these questions are answered - sort of.
Nothing is straightforward.
I won't spoil it, but I will say that the way they are answered is brilliant. To give a simple trite answer to the latter question would betray the spirit of this story, and fortunately that is not done. This is a story about horror and beauty, about our search for the truth within ourselves. It is wonderful, and promises wonder to come.