I'm going out on a limb here by saying that I'm a fanboy. The limb of my respect is very strong and thick, so even Kip can climb out far above the colorful land below and never need to worry about breaking the tree. 
 Kip was always the underdog, and who doesn't love the underdog? His story is by far the strongest in the books, and it doesn't take a genius to see he's being set up for so many more great things. One shouldn't refer to the title of the series. The fun is seeing exactly how he arrives to that end. 
 Gavin took a little getting used to, especially because he rightly considers himself to be an anti-hero, while strangely devoting his life to doing great and even good things. It's an odd sensation to be gently held by a razor's edge between divinity and demon-hood, and be completely unable to see the distinction in yourself. Fortunately, we've got the color prince as a foil for gavin and then we've got gavin's current course at the end of the novel. I do feel nostalgic about him and his lady love. I've got a very strong feeling that things will turn out all right for him in the end. Of course, if Mr. Weeks ever reads this review, he might decide to spite me. :) I hope not. 
 Liv, on the other hand, is useful for seeing the other side, although I still think hers is the weaker reasoning, despite her growing up as a quasi-slave, abused by the system. She had no bones to pick with with Gavin or Kip, and personal loyalty has often been known to trump ideology and charisma. A character like her is absolutely necessary for the story, but I have to wonder if Liv, herself, needed to be that character. I'm just musing about it. We are, after all, setting the stage for even more huge and god-like battles to come, so I will still side on Mr. Weeks decisions for her and I will certainly hope for a great deal of characterization for Liv to make what has come before much more worthwhile. 
 A Third and Fourth books will certainly paint all of the characters in different colors, because Mr. Weeks has already shown us that he is a painter that will give us many broad-strokes on his canvas, and isn't that particular about burying previous strokes under the new. Indeed, you can't do otherwise if you've chosen to have such a furiously quick pace in storytelling. I give respect, here. 
 I can't wait for the new books, of course. :)