The overarching plot of the series is this huge, fascinating arc that's not good-vs-evil as much as it is a question of WHO is good or evil, and why. This book expanded nicely on that question. I've never read so much adventure as philosophy or philosophy as adventure. It's the darkest yet in the series, but when you read it you'll see why. It all makes sense in relation to the big questions that McPhail is chewing on.