This one I found hard to rate. The story, characters, and dialogue are all very simple, which isn't always a bad thing, but at times they, the dialogue especially, were too simple, almost immature.
But I liked the way the author created the griffins, mostly Darkheart. These creatures had intelligence and could communicate with humans, but were still animals. Darkheart did whatever to survive, and saw no problem killing whatever or whoever to do it.
And I am interested to see where Taylor is taking the story after the events at the end of the book. I guess interested enough to give the next book a shot.