So, I realized one reason I was having trouble saying what the plot was for Book One was because I had not emphasized the plot of the first book over and above the other threads of the story (plots to be resolved in later books.)
I went back and did this, now the book is about (this is the factual description not the snazzy blurb):
A young woman wants to rescue her two friends, who have been captured by the Sons of Darkness, invaders from another dimension. While trying to get help, she discovers that the Earth and the whole universe are in danger. Vowing to save them, she sets out to learn more about the greater universe so that she can figure out how to do it.
Oh, and in the course of the story, she becomes a Creator and gains the power to make worlds and change fate. But nothing really comes of that until later books.
So…the threat to her friends is the subject of Book One
The threat to the Earth is the subject of Book Two and possibly Book Three
After that, it becomes a story about the Creators and their interaction with the general universe…and of the main characters personal quest to challenge fate (or undo the concept altogether.)