These books are a retelling of Milton's Paradise Lost.
It is kind of like Wicked in response to the Wizard of Oz.
Every now and then, a paragraph will illuminate the situation. This is from The Subtle Knife:
"There are two great powers," the man said, "and they've been fighting since time began. Every advance in human life, every scrap of knowledge and wisdom and decency we have has been torn by one side from the teeth of the other. Every little increase in human freedom has been fought over ferociously between those who want us to know more and be wiser and stronger, and those who want us to obey and be humble and submit." (p. 320)