We didn't see much of most of these characters except John in the second book in the series, and it's good to have them back. Sig and her friends would have been completely capable of carrying a series before John hit the scene. The whole cast is interesting and most are quite thoroughly developed. I only say most because there are one or two who are more sidekick than lead material. It's refreshing that the action is not all about John.
But when it is about John, it is of course brilliant. John has lived a long time and studied his field well. This series draws from a wide variety of mythology and folklore, and John's explanations pull readers into the world easily. He's also just the right sort of wiseass to anchor this kind of the series, but he is an adult. He's a living contradiction: werewolf and Knight, loaner and pack animal. But in his way, he has his act together. I eagerly await the next in the series.