Haven't read the prose, and I come at this from the perspective of a comic book fan.
I think the story is too incomplete to judge right now. And that is a very serious concern. If that last page was the cliffhanger to a monthly, I'd be fine...but I have no idea when the next book will be out, so it ends up just sort of lying there. Hopefully, it will read better as a whole, though even then, I agree with sentiments from te others here; the police woman's story, to me, was too abrupt.
I actually liked Khryss, though, if only because she was So different from what I had expected. I actually wish we had had more scenes of her and Kenton.
(The fact her colour scheme and arrogance reminds me of Trixie might make me biased.)
The artwork has a mixed reception to me. I definitely agree with characters being samey; I legitimate find it hard to tell which sand master is which.
On the other hand, there was a vibrancy to the darksiders, and I liked how the magic was presented. It really did lend itself to a more visual take, I think; it emphasised the difference between the showy magic of the masters, and Kenton's smaller, cleverer uses of it.
Two points I will say though. Firstly, Kenton is a deadringer for Connor Hawke, which amused me. And second,as accurate as it is, I wonder if perhaps some liberties should have been taken with the Sand Master uniforms. I like them -don't get me wrong- but the look of the costumes, the settings and Kenton's parkour in collecting the spheres reminded me a lot of the Assassin's Creed franchise.