"Straight Edges could take your soul."
the core of Asaro's story hangs on this incredible opening line. Through the course of this story, Asaro explores the idea that succumbing to hardship and fear can slowly make you less than human, and that you are only able to overcome hardships (the metaphorical "edges" of life), by facing your fears and coming to terms with your doubts. By adapting to and accepting the reality of your life, without letting it drag you into despair. This is expressed in the story itself through the threat of the Edger Demons, who, in my mind, are allegorical expressions of the "demons" that plague the "edges" of our lives -- i.e. our doubts and fears.
To make things even stranger, Asaro uses the idea of linear vs. non linear mathematics as a basis for the Edger demons' magic and their ability to control humans. The demons draw power from straight lines, or rather the equations that define these lines. The only way that the main character, Denric, can escape these demons is by using non-linear mathematics, the math that defines curved lines.
I know, it sounds dumb so far, but bear with me. The idea that non-linear math trumps linear math because it is of a "higher order" bears out into the overarching theme of the story. By not only using curves, but by embracing what they represent (flexible, yielding, soft), Denric is able to overcome the linear magic that traps him. Ultimately, the idea here is that flexibility, adaptability, and the willingness to face adversity overcomes the unyielding, yet also horribly rigid, strength of the Edgers. He gains his freedom by being adaptable enough, yielding enough to face his own inner fears and doubts, which in turn allows him to overcome the influence of the Edger demons.
Apologies if none of that made any sense. I'm still fighting off a bad cold, possibly the flu, so I don't think I'm on top of my game (not that my "game" is very high, but nonetheless).